Mainly what MM2X does is check EKiller and revenge things. Mega Gengar sets have shifted to being more anti-EKiller than they were initially, thus Gengar has seriously encroached on this niche. Mega Salamence was already in competition with MM2X as an offensive EKiller check to begin with, although you could make an argument that MM2X is a bit more defensively sound in this role as Stone Edge is everywhere and Ice Beam exists. Only other thing MM2X might do is effectively lure something out and smack it with specialized coverage, although certain Pokemon are able switch in with minimal risk regardless.
As for the second question I've got only one squad, an offense team, that utilizes it in a way where it doesn't feel forced.
As for the second question I've got only one squad, an offense team, that utilizes it in a way where it doesn't feel forced.