If Fane cast Mosquito Swarm on anyone, he will heal himself. Mosquito Swarm is a damage/self heal skill. Blood Sucker heals undead as well as everyone else. If you choose to do Blood Rain, the blood could be used to heal Fane.
I had to do some playing around and have only done this in the Definitive Edition. Any healing on a character with decay on them, should injure them. I tested this on a lich character (undead elf, Summoner + Necro + Geo) I have. Indeed when I put decay on the character and then cast Blood Sucker, the character lost health. The same can be said, if an undead is decaying, poison will injure them. However, while decaying, the lich cast Mosiquito Swarm on a different character and be healed from Mosquito Swarm. Either that is not working as intended or Mosquito Swarm is a quite powerful little spell.
I read something that stated all physical armor skills scale off Geomancy. Thus even a Necro skill like Bone Cage and the Poly skill Heart of Steel will both scale off of Geomancy. Likewise, all magical armor skills scale off of Hydrosophist.
All this talk about decaying made me remember the skill Decaying Touch. If you choose to have a melee character with intelligence as the primary attribute, Decaying Touch is practically a must learn. Actually, that makes a fantastic combo with Corrosive Touch and Blood Sucker if you have an opponent standing in a pool of blood. Just use Corrosive Touch (1 AP), then Decaying Touch (2 AP) and follow it up with Blood Sucker (1 AP) if you were able to set decaying. That is a total of only 4 AP and the Blood Sucker at the end should do some nice damage. Oh wait, if you are in the pool of blood with your target and have Elemental Affinity, that combo will only be 3 AP. Yes, I did test this out with my lich character and it worked great.
By the way, thank you! Without you starting this thread, I would never have thought of that combo. While it doesn't do the magic damage you want for the character, it fits within the build and does crazy damage. Blood Sucker doubles as a self heal and party support, so it should already be on your bar for the build you have in mind. That means you are really only dedicating 2 memory points to have this option available. Other than that the rest can go into party support and magic damage skills.
