I like simple solutions. If somethings broken i just use some 'x per x' type of formula to nerf it; perhaps x minutes per level,l or x damage per ability bonus.
For critical fumbles i simply deny dexterity bonuses for the next round. It is a simple house rule that sorta makes since and keeps the fun part of rolling 1s.
For nerfing casters i would say one of the easiest ways i heard on this thread might be to double ALL casting/construction time/cost, etc. Enforce v,s,m and weight allowance strictly. Those sorts of things would nerf a fair amount of the broken.
How 'bout. . . Limit every classes max spells daily by 1 or two? leave the same progression but less total spells per day at higher levels only nerfs the high level game.