During the quest Moments of Reflection the voice of Illidan can not be heard if talking heads are muted.

I whitelisted the specific areas on the map to hear what he had to say. These areas are:

Lorlathil (in Val'sharah)
Temple of Elune (in Val'sharah)
Nordrassil in Mount Hyjal

Perhaps these areas can be automatically unmounted if someone is on this quest?

I can't possibly maintain a list of quests/situations where people might want to hear the dialog, my suggestion is always to disable the addon temporarily during new patches/story quest content just in case.