Apocalyptic Delirium actually already gets a +5% boost to damage and to hit penalty per skill from sk 35-39.
Unless you're asking for even more of a boost.
Sure, in line with the fire/ice damage increases that were recently added (those on top of the 5% improvement per level, that is). Not married to any of these specifics, or skill levels, mind you, just throwing out ideas.
Couple of others, gained at some skill level:
Greater elemental resists, not related to protfire/protice, that would also include resistance to tier based elements
Max strike, without the 3rd "swing" that pallies are about to get...2 would be great<G> (since thruststrike was added at 31 or 32, makes sense to make this quite a bit higher, perhaps at 38, or perhaps post 38 in SDC
Ability to cast akro shield on others, or perhaps a reduced timer on akro shield instead