piranha1: The problem with that (bard/AA that is, not dumping mage levels) is that I'm thinking about the character with modules in mind, that are less combat-heavy, and rely more on skills and "RP" (like for example Tales of Arterra might be, from what little I've read about it), hence rogue is sort of a must, with biggest amount of points per level, and wide array of
class skills. (for the modules shipped with game, I'm thinking to just go barbarian and smash my way through them)
Actually, bard builds are a great choice for such modules, since bards get lots and lots of class skills, as well as an inherent bonus to lore (an often-used skill in story modules, that you don't need to invest in much further as a bard). Plus, you're the only one with Perform, and I recall several modules where that skill was used to allow you to do stuff.
It's true that you get (far) fewer skillpoints per level, but with a 14 intelligence you still get 6. You need Tumble and Spellcraft (but the latter again is a skill people often check in modules) and only need a modest investment in Lore and Perform to be effective at those, so that leaves plenty of skillpoints for stuff like persuade, bluff, listen or search.
piranha1: So, maybe I should ask another question: Which class should I mix a rogue with, to get a good assortment of skills, and a decent combat character? (as some fighting will happen in those modules anyway, I think)
Quite a lot of fighting, actually. Even the RP heavy modules I know tend to include quite a large number of battles. It's been years since I played the Arterra modules, but they had quite a lot of it, actually. (Although many encounters were optional.)
The few exceptions that come to mind are Almraiven (though not so much the sequel), Honour among Thieves and similar rogue-specific modules, (You are stealing stuff, not killing stuff. Lots of fun, by the way.) and Excrucio Eternum. (but the first module in that series has quite a bit of hack and slash in between the story bits.) Even the almost entirely dialogue-based whodunnit mystery Black Thorn has a tough epic level fight at the end. (Well, if you succeed, that is. I've failed that one almost as often as I've succeeded.)
The thing to bear in mind about these modules is that they are designed to be played with any kind of character. So mostly, the skill checks will NOT be designed so that only a rogue with maxed out stats can make them. So as long as you have a moderate investment in a skill, you'll almost certainly meet the requirements.
Anyway, class combos that work well:
Rogue/fighter. This is the simplest combination by far, but it just works. Fighter levels mean your rogue can use heavier armour and shields if need be, as well as making it much easier to deal with sneak attack immune foes. The rogue levels meanwhile give you tons of skillpoints to play around with.
I like the version that has mostly rogue levels, wears a chain shirt, uses a shield and is strength based. Makes for a neat swashbuckling swordsman archetype. With only a moderate armour check penalty, you'll still be able to sneak and do rogue-ish stuff, but you're much better in a straight up fight.
If you want you can add in a level of shadowdancer to really increase the utility of your sneak attacks, but you should be careful with that in high-level modules, since it can limit your total number of attacks per round, depending on how many fighter levels you have. This approach works better with dual-wielding characters, since you really want to maximise the number of sneak attacks you make. But you'll hate fighting undead.
Other variants such as rogue/barbarian and rogue/ranger work just as well, depending on what exactly you want to do. This combo works well for lots of races, but Humans and Halflings have the easiest time avoiding multiclass penalties. Elves do get a neat permanent search mode, though.
Bard/fighter Same idea, only less stealth and more magic. Fun character. You should only take 1 or 2 fighter levels early on, but since bards don't really get anything useful past level 16, you can take some more fighter levels then. You're a bit lower on the skills, but you should do alright.
Bards are surprisingly strong and effective characters, thanks to their buffing spells and excellent bard-song and curse-song abilities. The fighter levels do help a lot in reducing the squish-factor, though. I find this character type works best when just wearing heavy armour and shield, having a high strength and taking the Still Spell feat or just not casting any spells in combat at all. (You can take the armour off to cast buffs) But the lightly armoured dex-based version also works quite well.
Human is by far the best race, because you really want that extra skillpoint per level, and very few other races can avoid multi-class penalties. The bonus feat won't hurt either.
If you want, you can later add Red Dragon Disciple levels, which makes for a very strong character. But that will give you fewer skillpoints, and bard abilities are a lot more fun to use than just having a huge strength score, so I typically leave that until epic levels when I already have all the spells and such.