You really can see the lazy battle design in T7 when such a broken mechanic is left in and unpatched basically telling people to deal with it.
I've only seen what you're talking about happen 1 time and that wasnt a dps related issue, was just because we had tried stacking renaulds and the first one we stoned woke up before a long healer voice since we werent killing it (so we never tried stacking again) but we do hold damage at certain spots so we arent going into adds with a shriek out
If you push it past the trigger % too long after a voice, Renauds will wake up before the next voice. You'll then be forced to kill the Renauds, and there won't be another Renaud that spawns in time before the next shriek. Basically a wipe because you didn't wait for a voice and pushed it to said % before a voice went off, throwing off the "timers" that control the gimmick.
This isn't a problem if you break the ToS and you can see the % of the target, but SE implementing a mechanic where you have to push at a certain % when you can't even see the % is stupid.