I just checked out the tier list for 3.5e on 1D4Chan (which links to the original tier list forum discussion
), and the sheer dominance of spellcasters in and of itself is one good reason I'm glad we're not using 3.5e. I don't want to play a spellcaster. I don't want spellcasters to be stupid easy mode while my preferred class struggles a lot. Actually, one thing I loved about DoS2 is that spellcasters, while having their place, were not ridiculously dominant.
I can't comment on the complexity, but at the same time, I don't care. I'm of the mind that having one type of PC (spellcasters, ie wizards, artificers, clerics, etc.) able to run rampant over everything while other, potentially equally interesting options (physical classes, ie fighters, rogues, rangers, etc.) have a much bigger uphill climb does not a great game make. That's one reason I'm damn glad that 5e is being used over 3.5e.
(ps, there is a 5e tier list here
, and it seems like even the highest tier classes in the phb don't break any campaign in half, unlike 3.5e)
(pps, google linear warriors quadratic wizards if you want to see this phenomenon explained in more detail)