I also considered butterfly effect, but with two anti-matters and a druid I think there's already enough entropy. Plus, sometimes you don't have a good target, if you use it on an otyugh it loses it's devour ability. So steal is better in that regard. But in a different version where you have more low attack creatures butterfly effect could work well.
Well, for one thing, we have two otys in this deck, and when I use one, I rarely have need for the second, unless I draw it early enough when it doesn't matter much anyway, since quanta is more than likely to few to play a second one soon. Other targets are mutations you can't work with directly, but could give this effect to, but my preferred target, as I said, would be the ash of a so frequently targeted phoenix. I don't per say see a lack of possible targets, but yeah... quanta.
But in my opinion, in some fights you won't use antimatter, early or otherwise, and would have the time and need to play the butterfly effect. At other times, you won't play butterfly effect because you won't need it.
As for two quints, like you said that would make it a bit heavy on Aether, plus fractal also helps you protect your creatures (strength in numbers). But two quints could still be good, perhaps take out a shard of gratitude or anti-matter. But, there are only 3 creatures that you'd want to quint (until you made more creatures with fractal or mutating), so you'd risk drawing 2 quints with no good targets for them. Perhaps a bigger deck which is similar could use 2 quints, and also more creatures, like a firefly queen.
Yes, there's strength in numbers, but that doesn't mean we should depend solely on those numbers. If we're building an anti FG deck, then I believe there's also strength in your ability to adapt to a situation, and in some cases, you'll want that quinted oty out now, rather than hopefully fractal two turns later, right? But always the actual enemy is quanta...
But I'll definitely not take out a SoG, since in my opinion and experience, 3 is kinda the minimum.
How thoroughly have you tested your version of the deck? Can you say that quints are more or less obsolete with reasonable certainty? If so, I'll leave the quints out.
Oh, and sorry if you think I'm being a pain, I just want to try to get as many areas covered as possible.