Having JohnQT play initiator to help with midrounds actually hurts them, and the adjustment is probably why they sucked earlier
Zellsis is obviously one of the midrounders and was initiator (or the sentinel on like icebox, but KJ is more of a mid leaning agent on that map)
Anyways, SEN becoming stagnant in the midround, is because Zellsis is simply the better midrounder, and he's now playing away from the pack.
I don't see a reason in keeping zellsis if you're going to continue to struggle calling against top teams, he offers way more value in the initiator role than JohnQT does
Either JohnQT Sentinel, or sign a sentinel who can provide more value, since Zellsis' role has diminished