The Resists one gains from Resist Spells are actually the least important part of the skill, now. However, they are pretty convenient, like when you're trying to get dressed after a rez and something takes an interest in giving you another deathrobe. In such a case, those 40 or so resists can keep you alive long enough to get a close wounds or greater heal off as you dress - or at least run away.
Consider also that nearly everything requires mana. The effect of the mana drain and mana vampire is based on the caster's Eval, minus the target's Resist skill.
This means that if you have higher eval than the caster's eval, you will only be inconvenienced, as opposed to being totally shafted.