I've done a lot of playing wit Nissa and Jace. I stared Nissa because I'm a green Mage in mtg paper, but found that all her cards cost too much. I think they designed the green cards with using Nissa abilities in mind (the gain Mana abilities), but all that did was make you reliant on her ability to cast your underpowered creatures.
I've found Jace to be a powerhouse. His creatures have great stats at low costs and a lot of them are flying. His abilities make attacking favorable, and there are a lot of "drain Mana" cards as you've mentioned that straight luck your opponent out of the game. Green may have "fat monsters", but blue has multiple creatures that bounce, so you get utility AND a body. On top of that, if you have a SINGLE removal spell you can just cast it every turn using his 2nd ability. "Turn to frog" in particular is insane to recur.
From what I've seen of the cards I own (I've even spent a little $) Jace and Chandra seem best, with Gideon being ok and Lillian / Nissa being terrible. I haven't even faced anyone in pvp who used a deck other than Jace or Chandra so I think there's a real balance problem right now that will need to be adjusted. You can't have 1 color getting 6/6 for 10 that bounces another creature while another gets a 6/6 vanilla for 14 and expect people NOT to gravitate towards the cheaper and better cards.
Those are my observations so far.
Support - I couldn't find any notable support cards.
Oh boy, you might think, this is black which means creature destruction, life drain, ressing zombies...and you'd be right...sort of. Except all of that is really tedious and extremely mana inefficient. I gotta say Liliana might be decent, but she is a LOT of work to play, and you need a lot of good cards. Her starting deck is godawful. If you stick with her she is...decent. But very, very slow. One of the worst at low levels however, with abilities that don't really do much of anything. Everything costs WAY too much, and likely you'll die before you can even get a few creatures out.
Corrupt - this costs too much. Discards 2 (or 3 later on) cards for the price of 1. Not bad, but unsustainable. Good if you can catch a big fatty.
Grave Mist - this costs too much. 1 damage to all your creatures for 1, 2, or 3 damage to all opponent creatures. This is better, and can be a board wipe if you hold onto it.
Raise Dead - this costs too much. See a trend here?
I gotta say despite trying to play this deck I don't have many good creatures for it. If someone has input on some wow creatures please let me know (uncommon/common only, maybe a rare!).
Blood Cursed Knight - this costs too much...but if you play the whole disable thing, is a good way of maintaining your health. Still a 5/4 for 17 is painful to bear.
Catacomb Slug - 17 for a 2/6? What? This costs too much.
Possessed Skaab - pretty expensive for a 4/3, but at least it lets you return one more super expensive creature...to your hand. Sigh.
Shambling Ghoul - 6 for a 2/2...jesus christ. At least this is a zombie, so you can combo it with your res.
Undead Servant - 12 for 2 2/2's...I guess you could do worse. At least these are all zombies too.
Deadbridge Shaman - 8 for a 3/1, thank god we have at least something that is -sort- of mana efficient.
Fleshbag Marauder - thank god! This card is fantastic even without any effect, a 5/3 for 10. With its effect however, it is a great way of removing creatures. Should be in every deck.
Black creatures are a huge disappointment
Consecrated by Blood - this costs too much (more than a 3/3 or even 4/4 with flying would)..but it gives regenerate, which is nice. Decent on a creature with lifelink or can swing for a ton (or both!)
Cruel Revival - a very hard to use spell, it requires 1) enemy has a nonzombie AND 2) you have a zombie (non token) that has died in the past. So...this being your only main removal spell, it is unusable unless you cast your terrible efficiency zombies, AND get them kiled, AND they're only returned to your hand. Sigh...
Necromantic Summons - I am unsure whether it requires your opponent to have lost a creature or not, but if not, then this is a very good card. It is pretty good regardless, esp if you can ping one of your opponent's little creatures right after you lose a big one.
Reave Soul - decent against decks that like to stack little creatures, or those with weak creatures with strong effects. Also good to combo with Necromantic Summons.
Support - I couldn't find any notable support cards.
I underrated Murder Investigation initially. Combined with Gideon's ability to bolster creatures and give them vigilance, you'll have a blocker ready for as long as Gideon had 3 loyalty.
Some Rare/Mythic cards I have found that are not mentioned previously that I find useful.
Unholy Hunger (8) - Spell -Destroy target creature. If there are 8 or more Black gems on the board, gain 2 life.
Graveblade Marauder (15) - 4/7 Deathtouch, Berserker - When this creature deals combat damage to a planeswalker, your opponenet take 5 damage.
Despoiler of Souls (12) - 5/2 Creature - When this creature is destroyed, if you have a card with at least 3 mana, you lose 3 mana and this creature is returned to the battlefield.Oh boy, Liliana actually gets to do stuff, those rares actually look pretty good. I currently play her as a lockdown/lifeleech deck with the mythic Demonic Pact (level 4 Liliana lol), that deck is good ONLY for storyline missions where no other lockdown works, esp ones with high creature damage
Ravaging Blaze (6) - Spell - Deal 4 damage to target creature. If there are 8 or more Red gems on the board, deal 4 damage to your opponent.
Scab-Clan Berserker (19) - 6/6 Haste, Beserker - Renown 3. Whenever your opponent casts a spell or a support, your opponent takes 3 damage.Ravaging Blaze is pretty much just strictly worse than Exquisite Flamecraft, and only barely better than Lightning Spear. Scab-Clan berserker is worse than Iroas's Champion (and more rare) in pretty much every scenario except where you really need that haste. Even after renown, she is a 9/9 while Iroas's hits for baseline 8 damage.
Hangarback Walker (25) - 8/8 creature - Whenever you match 3 gems or more, summon 1 1/1 Thopter with flying. When this creature is destroyed, summon 8 1/1 Thopters with flying.
Sheesh, so hard on Lili.
I'm sure you can make a black deck that does well (very well) in both pvp and story, but the problem is the other planeswalkers can do so much easier with fewer rare cards, and at lower levels. So this is why I rate her so poorly. How many of the really good things you mentioned are rares or above? While Chandra/Gideon can win hands down with no rares at all, and Jace only really needs ONE of his many amazing rares to work.