they should never be removed, just tweaked.
a 100% reflect spell? Sure, but dont let it last forever, thats bad game design. Some enchants should simply have a hard-cap. You can't fix AI against reflect/absorb/levitate. (whats a wolf or troll gonna do vs levitate?)
Spells on the other hand should not have a cap. 100% reflect/chameleon spell that lasts a little while and takes a ton of magicka, sounds great and tactical.
Combat seems pretty important in Skyrim, they don't want to make combat trivial,
I'll bet anything that enchanting permanent 100% effects will not be in.