Necro Tech II: How good is it? What's the game plan?

Last night I played necro/balance/blood. Having necro units was nice. Graveyard helped keep some key units in play and massing skeletons. Then when your graveyard gets wiped I used a combo of bloods multi haste and the tech 2 u sacrifice to bring a fallen hero in with max lvl. Which I used necro so I could also play a discard pile unit 5 gold or less. Picked skeleton lord. And used balance peace spell to buy myself rounds without being attacked to build up more skeletons. Lucky opponent did not have mass clear spells. Balance hero lvled just enough to also give skeletons 1/1. And of course long range. At one point I came out of my peace with 6 4/4 skeletons 2 skeleton lords. 3 heros. Pretty much cleared the board FTW. My only iffy question was the tech 2 to sacrifice to bring a hero out. It doesn’t say if you have to meet requirements or not and I didn’t have hero hall or tech 3 building. Thumbs up or down move? Worst case I would of attacked with blood hero before the sacrifice to kill em then brought out necro. Same outcome.