Ok, just to confirm... we're not talking about game mechanics being bugged, we're not talking about a class or ability doing something it shouldn't, or even about players abusing something unintended, right? We're talking about an add-on, and an add-on working as it did in the expansion as far as I can tell, since you gave no argument saying otherwise, making this a proposal to change the server so an add-on can do something it wouldn't, correct? So players in the expansion dealt with this normally, without any complains beyond the everpresent "I don't like this, it makes me lose so it's OP" and similar, as they either didn't have the add-on or if it existed this simply didn't work already, yes?
Could the issue here be your dependency on an add-on that doesn't works fully in the expansion instead of the server needing any "fix"?
But if not being able to use a specific part of a specific add-on, on one specific expansion where it apparently wasn't meant to work, against specific classes, using a specific ability, is reason for you to leave, have fun out there I suppose.