If I were re-doing things, I'd errata the uber spells and make magic resistance more valuable. Allow ward saves and magic resistance against pit/dwellers/purple sun, stipulate that units with mindrazor use their unmodified strength for armor save modifiers, and allow magic resistant units to either get a save against hexes and other non-damaging spells or simply return to the old system of bonus dispel dice. There's no reason to overhaul the whole phase or to add a bunch of complex new rules. The next round of army books will almost certainly nerf or remove the focused rumination, sacrificial dagger, etc. Just fix what's broken and leave the rest.