I just spawn sort of 'ghost' frames that mimic my arena frames style
https://github.com/Strigoy/MonoUI/bl....lua#L339-L416
and monitor ARENA_PREP_OPPONENT_SPECIALIZATIONS event to get the class/specialization, then hide them when ARENA_OPPONENT_UPDATE fires (the actual arena frames appear).
MT frames seem to function as they used to, for me at least.