While this is an understandable move, it has more to do with arranging the roster to have everybody on their primary comfort roles than a lack of performance from the players. Equinox was always an easy target for blame with the "4 flex" setup that GFE started the HGC season with, but keep in mind that GFE signed him with full knowledge of his lack of experience on the main tank role.
Prior to picking up Equinox, GFE had been in a rough spot where they had severely under-performed considering the hype around adding fan, bkid, and creating the kind of super roster that everyone expected to take one of the blizzcon spots for NA. It was only after adding Equinox, despite his role-swapping to tank, that GFE became known once again as a power-house team.
It was an interesting experiment with the mass flex team that worked for a time, but I imagine GFE will opt to go with a more standard team composition going into the 2nd phase. Considering Equinox was a large part of that team becoming a juggernaut again in the first place, and that he intends to return back to his natural role on melee assassins/shot calling, I think he will be one of the most valuable free agents a team could pick up during the off season.