As long as you make it a point to kill everything yourself and do all of the sidequests, then DA:O is a breeze. Make a Rogue that uses two weapons, has tons of Con and high Str, and severely increase your lockpicking and pickpocketing. Give your party orders that will keep them the hell out of the way (I put my fighters on missile duty), then sneak into every ambush and chuck lots of bombs while invisible (the AI running the baddies is so dumb they'll just stand there and take it). In addition to the extra XP from pickpocketing and lockpicking, you get tons of extra XP.
The dragons are hard monsters, but the trick with them is to go try to kill Flemeth at a earliest opportunity. Yes, she'll incinerate you, but from then on the High Dragon enemies in the game are locked at your ultra-low level. Go elsewhere, do a ton of sidequests, level up, get some fireprrof armor, and then go kill her. The Dragon guarding the Urn shrine will be a breeze too. When you get to awakening, all you have to do is spend your cash on the electricty-proof armor, and you'll poof the Queen of the Marsh in no time, too.
Again, make sure you kill them before your party does, so you get the XP, see?
People like mages, which are fine for sitting back and blasting things, but in the mean time your fighters are scooping up XP by killing easy stuff and leaving you in the dust, and then there's all that free, easy XP you get from opening chests. Sorry, mage players, I love blasting the shit out of things too (especially elves and their equivalents in other game systems) but the Rogue's king at earning cheap advances.