I would like to ask which character you guys consider best for SOLO game IWD2? I passed it with monk but there is probably better ???

Any class can do. Sorcerer is probably the most comfortable to get through.

Something armed, armored, hardy, built like a tank, likes to hit things, has a modest selection of buffs and heals...

I'm thinking ... paladin?

Barbarian, Sorcerer, Cleric, Druid, Monk all look like good picks.
Fighter, Ranger, Bard, and Paladin look usable but are outclassed by the classes listed above.
Wizard and Rogue look completely useless for a solo playthrough.

The Barbarian stands out as the offensive powerhouse of 3rd edition. A single level dip into Fighter can get him his missing armor proficiency, his fast movement speed lets him kite more easily and makes him the best option for ranged combat as a solo character, and while raging he has very high willpower to resist deadly magic. Barbarian simply outclasses the other combat-oriented classes.

Sorcerer is the strongest arcane spellcasting class for a solo run. Sorcerer learns his spells automatically and is unaffected by the IWD series' absolutely draconain limitations on scroll availability. The only trick is that he's vulnerable to being ambushed due to how squishy he is... and IWD2 loves its ambushes. All things considered this can be worked around and if you want to play an arcane caster Sorcerer is your best bet.

Cleric is your best choice if you want a balance of spellcasting and melee. It has both self-sufficiency in combat and buffing power that is quite frankly unrivaled. Its spell list is versatile and powerful, allowing it to do whatever you want it to. While it's nowhere near the borked brokenness of its pen and paper equivalent, it's still got arguably the best overall showing of any class in the game. You can basically say all the same good stuff about its nature-themed counterpart, the Druid.

Monk is an interesting case. In pen and paper it's arguably the weakest class in the game, but IWD2 was incredibly generous to it. Monks can have absolutely unrivaled defenses in IWD2 and their offensive power doesn't slip too far behind the other melee classes. Overall, it's an interesting choice and if you want to see the Monk shine then IWD2 is probably its best showing of any of the 3rd edition CRPG"s.

Fighter is entirely outclassed by the Barbarian, and is useful only as multiclass fodder. Take a few levels for proficiency and bonus feats, then never look back. 4 absolute maximum if you really want weapon specialization. Ranger is in a similar boat; if you want spellcasting... look elsewhere. As a melee character, it's strictly outclassed by Barbarian. Bard and Paladin are outclassed by the Cleric, which is just plain better than them in a solo run. Bard isn't bad if you have a party to buff, and Paladin isn't bad if you have a party to buff you, but if you need to be a one man party... Cleric just leaves them in the dust. None of these classes are unviable, per say, and I'm certain they could reasonably win a solo run. They're just outclassed by better options.

Wizard and Rogue are the only two I'd say are flat-out useless. Wizard is absolutely crippled by the lack of scroll availability, meaning he effectively does not benefit from being overleveled. Rogue, meanwhile, is so outrageously underpowered in IWD2 that it's not even worth a party slot on a 6-man team. On a solo playthrough, it's second only to the wizard for unsuitability.

I don't know much about the sorcerer because I never played one, but I agree that a barbarian is viable for solo play.

I had a question regarding taking one level of fighter to get plate. Plate restricts your dexterity bonus to AC. I think the most you can get from plate is a +2 bonus. You'll need a high dex anyway, so why not just stick with medium armour? Is the AC from plate enough negate the dexterity penalty you'll get?

You said that rogue is useless, but what do you think about combining barbarian/rogue just 'till you get evasion? Think about it. Evasion combined with a high dex and constitution means your barbarian can take a fireball to the face like a champ.

But yeah, barbarian is incredibly powerful; with it's damage resistance, to say the least. Play a barbarian and your foes become clerics. They'll see you bringing judgment day and all they can do is say their prayers.

No, the AC difference between light armor and plate armor is just too big. Nothing wrong with using a suit of lighter armor if it has a useful secondary effect you want, but in terms of raw AC platemail will almost always be your best piece of equipment. If the game had some bigger dexterity boosting items it might be another matter, but you simply can't get your dexterity high enough to overcome the advantage plate has over lighter armor as a barbarian. Fireballs simply don't deal enough damage against a high HP character like a barbarian for it to matter. Evasion is still a good ability, just not worth a two level dip that costs you a point of attack bonus and gets you nothing else worth mentioning. In NWN where skills are more important and sneak attack actually functions correctly it's another matter, but in IWD2 I think the Rogue is complete garbage.

A rogue could be quite fun to solo. Just be aware that the most important stat for rogues is strength which should be maxed and raised at level up. Pumping up the use magic device skill will add a lot of flexibility.

That is rather unusual; I don't think I've run into that being the case before. Then again, I haven't really seriously used rogues in many games or at least not paid attention to the damage they do.

I suppose it could be important in Wizardry 8 if you want backstabs to do good damage. (Strength gives up to 100% extra damage, which is multiplied by the backstab multiplier.)

In Bard's Tale 1 and 2, Rogues are useless, and in Bard's Tale 3, the damage bonus from Strength is irrelevant because your Rogue's backstab likely has a 99% (actually 255/256, I believe) chance of being an instant kill.

In IWD 1 a fighter/thief's second best (or best, depending on what you're planning) stat is strength. 19+ strength gives you a pretty big bonus that the thief's backstab multiplier complements beautifully.

3rd edition Rogues are a very low damage class, and are heavily dependent on being able to either reliably land sneak attacks or gain huge amounts of bonus damage from magical weapons enhancements. IWD2 inexplicably nerfs the sneak attack rules into uselessness, and the campaign is incredibly stingy on magical weapons (about as bad as it is with scrolls, to be honest) so you can't rely on that either. This means there is only one way to get a decent amount of damage: invest heavily in strength.

To put it bluntly, a Rogue with a 1-level dip in Fighter and maximum strength using a greatsword deals more damage per hit than a max-dexterity Rogue who is using a short sword and getting sneak attacks on every hit. In other D&D CRPG's the "strength vs dexterity" debate for Rogues is actually quite nuanced, but since IWD2 nerfed the sneak attack rules there is literally no redeeming feature for DEX-based builds and STR-based just completely outclass them. In IWD1 you could maximize all your ability scores at character creation and get the best of both worlds, so there really wasn't the "strength vs dexterity" comparison. In IWD2 you will receive several ability score advancements over the course of the game and divvying them between two stats is just not a good idea so you will be forced to emphasize one or the other.

It's a little more complicated than that (and I always forget to keep this in account - *sighs and hands over my Power Gamer Card*): specifically, it appears that in 3E you want to leave your main stats ODD if at all possible - in other words, if it starts out even, use an odd number of advancements on it; if it starts out odd use an even number. If this leaves an odd point out, use it somewhere else :)

An odd base stat virtually always is more useful in 3rd Edition D&D than an even one. Yeah, it seems kind of weird - you'd think that bumping up another point is the way to go (after all, an odd stat gives no more bonus than 1 fewer point, while adding another one bumps you up to the next bonus, right?). If you didn't buff or use enhancement items at all, you would be right, mind you, but the rub is that you're going to use both. If you have an odd base score, an odd point in buffing bumps you up one more category; otherwise it is effectively wasted (and a +1 ability bonus item is entirely worthless if everyone has an even base value in that score! Also notice that ability-bonus items have a marked tendency to provide an odd bonus ...).

Obviously, you're trading baseline power for more oomph from bonuses, but given that base ability points are a precious and limited resource (hence why a major wishlist item for an IWD2 EE is the ability to dice for abilities as you did in the AD&D based games!) while buffs are a mere spell or gear slot ...

That does make a degree of sense, but IWD2 follows the 3rd edition version of the Bull's Strength and Cat's Grace spells (and other spells, for that matter) meaning whether their total bonus is even or odd is entirely at random. Furthermore, there are many items with even bonuses. I'd need to run through the game again to see the prevalence of even and odd numbers, but you won't always benefit from having an odd baseline. All taken together, I'd rather go with even so my baseline without magic items is ideal. This logic does not apply to the 3.5 CRPG's, where magic bonuses are virtually always even numbers. However, for IWD2 and NWN1 you are correct that this is a consideration.

In the case of the Rogue, though, maxing out your attacking stat is non-negotiable. The Rogue only gets 3/4 attack bonus progression, meaning your accuracy lags behind other classes. This makes it all the more important to maximize your attacking stat without diverting your attention elsewhere. For instance, suppose you have a Rogue 20/Fighter 4. This character has 19 BAB, whereas a Barbarian 20/Fighter 4 would have 24 BAB. Even ignoring the boost from rage, you're 30% less likely to hit than that character and can't afford to fall behind any more without being completely gimped. I dislike the "rolling for ability scores", and much prefer point buy. IWD2's point buy system is utter garbage, though; using the proper costing from NWN would be a huge improvement. That said, Paladin and Monk will suffer immensely if they can't take their dump stats down to 3 to buy 18's in their primary stats. Those classes were very underpowered in 3rd edition, and are only propped up in IWD2 by the fact that they can afford shore up their weaknesses with 18's in multiple attribute lines.

I actually dislike the whole "ability scores set in stone at character creation" aspect of D&D (every edition, I believe). I prefer games where your starting ability scores aren't particularly important in the long run, like Wizardry, Bard's Tale, and even some Might and Magic games. Or, for that matter, JRPGs like Dragon Quest where your stats can realistically grow into the triple digits by endgame.

+5 to hit (or to damage if you invest them into power attack) vs 5-30 sneak attack damage doesn't look like a totally bad trade.

IWD2 only allows you to sneak attack any given target once, after which they are immune to further sneak attacks.

Sneak Attack is a good ability in the other 3E CRPG's, but you need to be able to activate it consistently on every attack to get value out of it. This is literally impossible in IWD2, so it's not worth the loss in attack bonus at all.