Forcemasters can be a problem for any Warlock build. In the early game you don't float enough mana to toss multiple Drain Souls. I would strongly consider including an Enfeeble to lock down the FM while you and your Vamp walk around killing her battleforge, hand of bimshalla, and any other conjurations she has in play. Actually, Enfeeble is such a mana-efficient counter to any melee-heavy build in the game, that I try to run at least 2 of them in every Warlock deck that I play. (and if the other guy uses all of his dispels on enfeeble, now my ghoul rots and agonies are sticking)
Idk, I probably would just recommend not playing a Vamp against the FM. Her control enchants are very efficient against large creatures in particular, and sure you could try and stop those, but eventually, you will want to do something other than worry about Nullifying or Dispelling control enchantments. This is especially true if you're playing a mage who does not naturally channel for as much as the FM does and cannot afford to break even over and over on mana.
A combination of Bats, Imps and Skeletal Sentries works great against the FM, though small creatures in general are really good vs FM, since few of her spells are efficient vs them (particularly small fliers). Rots and Burns care not for defenses, and the little attacks either get through unchallenged, or let your bigger Mage or skeleton swings or attack spells get through.
Agree, Enfeeble is hands-down the best curse on a FM, especially once her Cheetah Speed is gone. Agony works great too, since it reduces dice on both strikes of Galvitar. Outside of Galvitar, the FM has a tough time dealing efficient damage, so if you can Slow and put 2 zones of distance between you and her, she's really hurting.
