I do not know any class which is buff dependent... least not mine. What I do believe though is arcane casters are 10 fold more efficient then other classes in a quest. There's no doubt about that... If you play well and have a well built melee then go solo a quest, then turn around and play on your sorc or wizard on the same quest - you'll finish much quicker on the latter than the former. The same player playing an arcane who knows how to play one will be more efficient then he is on his well built melee based character. Both are built to survive, both are built with decent dps but the versitility of the tools in the caster's build make the quest simplistic and his spells are easy buttons.