BH + Discord is a nasty combo that works well against non-rainbows.
But then there are two cards that can be nerfed, not just one, so why not nerf discord instead?
Say that discord can now only change quanta from a single type on its attack. Would this fix the problem without touching black hole?
Thus black hole could keep its ability as a rainbow killer and the two cards together could be made less powerful.
Of course, and this is just me, I find the long term quanta control of pest/fractal to give me more of a scare than discord/black hole.
Are there even many cards that aren't too strong if we go hunting for combos? Gravity shield + almost any buff = monsters that can't touch you. Steam machine + shard of readiness = free +3 attack every turn (+4, but since one wears off, only 3 stay long term per use). From what I understand voodoo doll and parallel universe make for a nightmarish combo, as well.
But, then again, I would also likely claim someone with pulverizer and black hole would likely be in a better situation than someone with a discord and black hole, even though its not exactly an amazing combo.
What's more, the BH/discord combo won't really hurt a non-rainbow much more than a discord alone. If I am running mono earth, once my quanta has been made into air, what do I care if you drain it or not? You get more health, but since I am running mono earth, I have a card that can get me 50 health, which is quite a bit better than 36.
But then, that is my point with the combo being "bad" for non-rainbows. All the damage comes from the discord mixing the quanta, not the BH draining up to 33 quanta I would never have used anyway, and likely not the extra health, which will likely be forgotten in the long run, unless the game was based on that health gained. Even then, there are other cards that could heal, as well.
It seems like a stretch to say BH is too strong because of a combo that doesn't do much more than one card alone, anyway, particularly when that one card is not the card in question.
Not as much as many of the replies, but, still, it strikes me as a bit odd to have a way that a card works well against non-rainbows involve a card that works well against non-rainbows.
It's like saying discord is great against rainbow decks because in a combo with BH, it will heal a lot and drain a lot of quanta. It's true, but its not a case for discord being OP.