80~85% crit is recommended because you want a decent amount in case your party offers none, and it gives more consistency. But going much higher is not recommended, because it will waste things like ice trap, grenadier buff, and the level gap versus lower level mobs. As with defense, every 1 level higher above mobs gives 1% more crit. So if you have 95% crit and are 10 levels above mobs, you're wasting a good 5% just there.