I did some Shulk testing to confirm my suspicions about Buster. I wanted to see how punishable Shulk's f-tilt is at various ranges, so I had a friend space f-tilts on my shield. The results were very interesting.
At tipper range:
-Both Speed Shulk and Standard Shulk could get punished by Little Mac f-tilt.
-Buster Shulk couldn't be punished by any attack that Little Mac had.
At blade range (as in, not tipper, closer to middle of the blade):
-Speed Shulk could get punished by Little Mac f-tilt and f-smash.
-Standard Shulk could get punished by Little Mac f-tilt but not by f-smash.
-Buster Shulk couldn't be punished by any attack that Little Mac had.
At close range (as in, close enough for Little Mac to jab):
-Speed Shulk could get punished by jab, f-tilt, f-smash, pretty much everything. Same goes for Standard Shulk.
-Buster Shulk couldn't be hit by jab, because the shield pushback was too much, but he could be hit by f-tilt. F-smash was *still* not possible.
I'd like to continue testing other characters (as well as aerials), but my conclusion is that Buster Shulk is flat out superior to every other Shulk by quite a bit, and Speed is rather underwhelming.
He only takes +13% damage from being in Buster now, compared to the +40% that he deals back to the other side. In exchange, he's much safer, and his attacks have less knockback--and this is an advantage rather than a disadvantage because it makes traps and followups easier to achieve.
Buster Shulk and Ike are both significantly overbuffed; the buffs were very inappropriate imo, and both are easily top 5 contenders with customs (Decisive Arts for Shulk, all moves for Ike). You can't punish well-spaced attacks from either character.