I get the reasoning and why you have suggested these. But slow immunity would completely destroy pvp. If wiz/tao couldn't slow warriors. It would cause a massive in balance in pvp. As the difference in damage between them classes and the speed in which the damage is handed out. Would just become a war only server.
Right now you stand in ice and a warrior has to risk coming in for you. Slow immunity means they walk in and 2-3 hit most people.
See wiz could stack enough damage to flatten a warrior, but while doing this you would have no defence and no hp. So a ranged hit or 2 from another wiz or a cop your fucked. Never mind if the war catches you. 1 hit and lights out.
Wiz/tao do not have the luxury of going all out ma/mc or sa/sc and still being able to remain healthy during battles. These classes rely on slow.
But hey that's just my opinion I'm sure theres 50 warriors who will tell you a different story.