Okay, so, for clarity. Expanding the ignore list - simple, probably. But do you have an actual proposition on how the GMs actively combat intentional harassment? That might help a bit.
Kheldians are both not mentioned and you appear to misunderstand how they play. Dwarf is not a 'tanker' role, you actively switch between human, dwarf and nova to rotate through your attack powers.
The answer will, of course, when it is an enemy group in actual 4* content be . . .
Five Corruptors, a meat brick (your flavour of choice), and two blasters. That's what endgame looks like, in CoH. You physically cannot use most CC in a reasonable fashion on 4* enemies.
It's entirely, on its face, stupid to nerf any portion of a CC set when CC has no place in Endgame content, the only place where 'balance' should actively be a dev concern.
Well, actually, you just don't slot Triumphant Insult because there are much better slotting options than chasing def bonuses on a taunt power, but Indy is of course correct as always.