I think you will have diminishing returns if you play more than one Raven's Crime. Loam has a big fat target on it post-board, so I understand having multiples is at least reasonable. Honestly, with Entomb I would probably play more copies and drop to singletons of Loam, Crime, and even 1x each of Nether Spirit/Bloodghast. You are only playing 2x Therapy, so the sac-synergy isn't a real focal point.
Crop Rotation could cause problems considering you aren't playing that many sources of green mana. I wouldn't play CR with less than 26 lands, maybe even 27 (Wasteland/Factory/Cabal Pit/Bojuka Bog/Tabernacle...these aren't lands, they are effectively spells.) It's a great instant speed trick, but I wouldn't ever play more than 1-2. Entomb with an active Loam does the same thing really, it's just slower.
I think you are going to be disappointed with Pernicious Deed with only 25 lands, and without any actual ramp. Yes it does a lot, but it's abysmally slow and doesn't kill PW's. Maybe 1 in the sideboard, but I've tried maindecking it and even with acceleration (I was using Deathrite Shaman) it was too slow.
I suggest this:
-2 Bloodghast
-2 Pernicious Deed
+2 Entomb
+2 Lands (Barren Moor + Fetchland is what I recommend)
I just noticed...no Hymns!!! How did that work out for you? I guess Brutality is the sub for it, which is fine. Brutality does so much for this archetype, I think it's a great addition to any pox deck.
If you are really having trouble with creature swarms, I would suggest 1x
Darkblast. Entomb really shines again at getting that available.