Other things can be done to help CW, but I'd like to second Zen's suggestion that the Carrion summonses be less expensive.
One thing that hasn't been brought up is the long term magic research issues for CW. Because of the population dying, I've found that even sages are too expensive to really use many of for research. Likewise, Black Dryads have poor research, are almost useless for CW (they can't lead the carrion beasts, and save for the rare Sagitarian Beastie, can't bless them), and cost upkeep.
Panic Apostates are _very_ expensive, have very high upkeep, and the few CW can afford will have
far better things to do than research - site searching, leading carrion beasties, and summoning more carrion lords/ladies/donkeys.
Near as I can tell, the only semi-viable long term researchers are the Carrion Ladies; bad research ability, but they don't cost upkeep. But given their expense (in nature gems), and the fact that they
could and possibly should be summoning more carrion critters, they still aren't very feasible as is :
Do you spend 16 nature gems for a bad researcher, or 25 for a Carrion Lord to animate more vines and rotting bodies, given that those are the bulk of your army, and they're slow to create. Either choice is bad.
Things might be alleviated a bit if the Carrion Commanders were either cheaper, or a little better. Or if the Black Dryads could at least lead 5 or 10 carrion critters - after all, they've lost some holy ability because of their exposure to the Carrion Woods, shouldn't they be able to command a few beasts? (Not necessarily giving them blood or death, but a minor form of the Undead Commander ability.)