So let's give you an even bigger advantage by allowing you a ward saves on top of that.. Even with your high initiative, plowing through 30 elves will still kill 5 on average. With a ward save, maybe no kills at all.Ogres have access to death, but Purple Sun testing against initiative doesn't scare me in the slightest.
I generally don't use vortex spells because they are too risky (due to the chance to hit me instead). But I can certainly use them. Why would I agree to gimp myself, while giving you an advantage? What do I get in return?
As for magic resistance, it doesn't currently work against those "test or die" spells. Only works against spells that cause wounds, not spells that remove models from play. Are you saying you want to change that to allow it to work against all magic spells all the time (like crack's call)? If you do, suddenly my army becomes OP. I field few units by design (or just two if I want a bunker army), which I can give now high magic resistance to everything. Magic phase gone. That's imbalanced too.
Besides, I am really resistant to changing rules. I've written about this earlier in the post. I don't like adding rules if we don't have to.