Decidueye from what we've seen so far has no clear weaknesses, there is a considerable amount of people saying there is nothing he can't do and i'm inclined to agree, Darkrai has seen a ton of success in arcade and this recent nerf hasn't seemed to hurt him that much as we have seen from Rubs at EGX, Chandelures damage and overall utility has been buffed quite a bit in return for a (Probably) needed nerf to minimize, her defense got considerably weaker but the smog changes make her ability to create space between herself and the opponent even stronger.
SM2's tools have been hindered quite a bit in the nerf to 6y and while the diagonal teleport is nice it hasn't completely sold me so i'll hold off on bumping him up until i can see it put into play, 4X cancel is gimmicky.