Best way to gather level 8 spell comps?

I have been playing on and off since launch but I have always been very casual and never done much end game content. After the Feb patch I was able to gather set armor enough to equip my 4 275's with epic 5/4 sets, the first time I have used set pieces. Up until then I also only used level 7 spells on all toons except my mage. Now I have 3 other 275's and 3 other 200+ toons I want to get level 8 spells on. DI drops comps but you have to pick and choose what to kill depending on class so it's hard to gather the huge amount of the rarer comps needed.

Anybody have some tactics for this?