Right, I’m going through (first one I found) [Casual] Nopethebard Demonology/Necromancy/Truth vs charnel_mouse Balance/Blood/Strength - #3 by Nopethebard with my thoughts:
Our plan: Not sure personally why we have replaced Disease with Truth, hopefully I’ll work this out as we go through the game. Main win cons are still Metamorph (weaker with quince though), and early game board control.
Opponents Win Con. They have an all round deck. Rook can be a bit of a stone wall, but otherwise they’re dont seem to have anything monstrous we need to plan around, can adapt as we go.
P1T1: We have the dream opening! Vandy + Skelejav + Haunt puts out opponent in a really bad spot, they cant really avoid us killing heros (esp with sac the weak + Deterorate both posibly in your next hand) would really like to see us play to our early game board control win con here.
P2T1: Predicatble Rook stone walls, (having the haunt last turn means we can easily wipe most of the board + get max Vandy here, HUGE tempo swing possibility lost)
P1T2: Summon skeletons is a big tempo loss here. This is not setting us up for a early game win con, seeing the hounds tech really feels like that is what we should be pushing too (personally I would like to see the Bone collectors first, we are P1, and the extra skele to auto defend with is really hard to pass up) Note: we cheat here only paying 1 gold for our tech 1 as a multicolour. Dark pact for the card advantage is also not a bad pick here.
P2T2: They are playing super gready, the fact we cant punish this as black is really worrying.
P1T3 We are down on cards and not teching at least 1 dark pact, this feels bad. Killing rook is nice, but the rouge feels like a bad choice, again not great for the tempo plays. WE have board control now, so hopefully we can kill that tree before they get use of it.
P2T3: not building a tech 1 here is so greedy… please say we can punish it.
P1T4: TQ is our game plan here it seems, mirror copies make sense. killing the tree before it got any value is super nice, but our hand size still sucks, would like a heros hall here to threaten Meta (esp since we want a tech 2 next turn). SHrine seems win more with our current plan, again dark pact to recover card advantage until we get out plan rolling would be good.)
P2T4: Rock and tower, thats not a good wall, but we dont have a lot to push through it, not that big a problem since we want to tech 2 this turn, but its a shame.
P1T5: … Im confused about our techs here. Banefire and Hallucination dont seem like good techs., we’re also not developing a board here, which really hurts our tempo plan.
P2T5: Tech 2 Balance is a not suprising, we are weak to fliers with Demonology. Tiny Basilisk removes any hope of Meta plays atm.
P1T6, decent play with the hand, Bone collectors are late, doom grasp is not the best plan to deal with fliers, working TQ means we’re just given up on our win condition, and we havnt teched/preped another…
P2T6: Tech 3 is a win con however. This is not a good spot.
In Summery. Black/Black starter is a colour that revoleves heavily around tempo and board control. Most of its cards/effects are best when you opponent has limited resources, knowing when/how to push is really important with this style of deck.
We also need to be aware of our own win cons. Workering TQ, not building a heros hall/playing Quince before early to get our mirrors really prevented us from winning, and we didnt take enough tempo early on to prevent our opponents tech 3. playing so many cards as black early on is not a problem, as we have dark pact to refuel, but we never teched/tutored for it, so our own hand size was a problem. Our tech plan did not feel planned, which means we did not have our techs when we wanted / needed them (for this sort of deck, would highly recommend planning most of the techs out in advance before the game, for instance:
Bone collector/Dark Pact,
Bone collector/Dark Pact/Hound/Shadow bolt.
TQ/Void blocker/Dozer
Free Speech/Dozer/Void blocker/Flex.
Hope this helps 
(Note I don’t play much black, due to the fact I prefer playing a value game, but most of this advice should be sound, other people who play black better can probs point out the mistakes I made)