Blinkicide is right.
Like most other RPG's here too combat XP is so excessive that it pretty much always thriumps any peaceful paths.
Which is why I look forward to Pillars of Eternity not having combat XP. A lot of people whined, complained and threatened about that, but it's really the only reason to properly give alternative solutions without putting one clearly infront of the other XP-wise...
Yeah, I was as well quite irritated about this. Evading some guards with sneaking. invisibility, etc punish you with quite a lot xp loss and there is no real good reason for that. Actually iirc even Torment had a lot of non-combat xp for different solutions to problems that made sure that you do not fall behind in xp for being to clever for combat.
I put this into the same category as the late and incomplete translation, missing dice in my collectors edition, only 2 companion characters, which are not fleshed out much, etc: Budget and time issues.
Makes me a little sad, but I am still very, very happy with the game, so what? Could be the game even better? Jup. Is it still better than Baldurs Gate 1? Yes! So I am quite happy and hope for the next Larian game which maybe does spend just a little more time and money on the polish.