Deep Gnome would be a terribly unfavorable class choice for a Monk. As kmonster says, they deal hardly any damage, so you really cannot afford to be a small-sized race with a strength penalty. If you want a Monk, go with a Half-Orc for maximum strength.
The one thing you're lacking is a strong dedicated single-class attacker. Due to the multiclassing, neither your Paladin nor Barbarian are going to get the maximum possible accuracy or attacks per round, so having a dedicated warrior-type would make sense. You could go with an archer like Engerek suggests, but that's really more of an IWD1 suggestion. Archers are very niche in IWD2, and I'd only recommend them if you're making a strategy out of using spells like entangle, web, and stinking cloud to prevent enemies from closing distance.
If you want to go with archery, single-class Elf Fighter is the way to go. The Fighter is basically the only class that's any good at archery, since the other classes cannot get weapon specialization (counter-intuitively, this means Fighters are strictly superior to Rangers as archers). For melee, Fighter/Barbarian is a nice mix, although since you already have one you could just as easily go single-class or with a Paladin if you prefer. Rangers are kinda underpowered in IWD1 and I'd avoid them.
As for the rest of your party, I would warn that your half-orc will likely suffer multiclassing penalties with that class combination. Favored class for half-orc is barbarian, meaning you'll need to keep your Fighter and Druid levels balanced to avoid taking a penalty. However, with this sort of class combination you really want your Druid to be your highest class level. To be honest, I think starting with 1 level of Barbarian and then multiclassing to Druid and never look back is the way to go. The Fighter class is nice for bonus feats, but if you're going Druid you really want the spellcasting progression more.
For the Rogue/Wizard, I've tried it out and to be honest I think you can just drop the Rogue completely. Thanks to the cross-class skill system in IWD2 you can still invest in rogue skills even without being a Rogue, and since these skills are intelligence-based Wizards can eat the cross-class penalty easily. I played a single-class Wizard as my party rogue, and I never had any real trouble with picking locks or disarming traps. Especially with the level penalty for being tiefling, you probably don't want to do any multiclassing here.
I've also run a Paladin/Sorcerer, and I would warn you that it's a lot harder than it looks to pull off well, and towards the end of the game it just falls apart completely and is no longer effective in combat (so you're just a Sorcerer with the defensive abilities of a Paladin). It's definitely doable, but keep in mind that in the long run you will be transitioning into pure caster playstyle with this guy.
