Did some poking around in Warhammer Online and I've come to the conclusion that making resurrection spells a 3-second cast and usable in combat would do great things to Battlegrounds. Terrible, yes... but great.
I think I'd make it 5 seconds, but I agree it could make things really fun. A reduction to healing-health ratios, increase in mana costs and ability to raise (with skill and stategy) sounds fun.
Especially since it could actually make dps idiots care about protecting healers. They might not care about nonstop heals, but the idea of never taking a trip to the graveyard might ring differently.