I thought the Hematophage perk was underwhelming, though not a bad idea. Blood packs have the same weight and health restored as purified water, but I don't think that's good enough. Here's a simple overview of how they compare:

Blood Pack without Hematophage
+1 HP

Blood Pack with Hematophage 
+20 HP

Blood Pack with Hematophage and this mod
+50 HP
+20 AP for 3 minutes

Stimpaks at level 33 medicine also heal 50 health, and jet adds +30 AP for 4 minutes, so I don't think it's particularly overpowered. Make sure to give me any feedback you have.