Hi! Just as a heads-up, this issue first occurred on Monday, and I submitted a fix for it this afternoon - once we got Reaper requirements refactor (that's fun to say if you roll your "R"s!) into RC.
I'm pretty sure the cookie tax for that ask is already off the charts, and this fix is currently in WIP QA, so I strongly suspect it won't make it into this Monday's patch notes.
With one working day to the end of the week, we're long past the RC cutoff. (News post has been written, localisation's underway, etc.)
But as noted, it's a visual bug in the Slayer counter/tracker - the cluster tasks are merely pulling the name of the first creature in the cluster instead of the cluster name. So in the meantime, it doesn't impact gameplay.