There are some things that result from the 14 level spell cycle and also from the way how armor gets weaker with every level.
Take for example a fury that only has a limited number of spells, the biggest is strike of thunder that you get with 22 i think. When you get it at 22 the 1000 damage or whatever it does is really a big hit against level 22 mobs. However at 31 it still is you main spell, and the mobs have much more HPs, so if you don't have increased your INT it looks weak against the actual mobs.
Also look at effective mitigation, if you get a set of mastercrafted plate for example at 22 for your tank you will have around 50%, at 31 it is dropped down to around 40%.