Less whining than the two posts above you, but still whining.
Aside from the last sentence, this does not belong in the Unholy DPS thread.
Warlocks had the exact same issues recently and a patch + hotfix (3.0.8) was released to fix affliction DPS and buffs being over written (I forget the specifics). It's too bad they don't actually do something like fix the bug or at least buff the other trees, did they think adding a cleave to Heart Strike would magically buff it's single target boss damage?
How many other classes have 1 spec for PVE? Warriors -> Fury, Rogues -> HAT etc.
My recommendation for fixing Ebon Plague is to simply make it a debuff on the mob that isn't a disease and make Crypt Fever go up and only affect the DK that put it up (so we'll see multiple CFs) and make CF provide a disease increase to that DK only.