I don't think their intent was for it to be an aggro dump, that was just the way for them to figure out the DA Tanking issue from earlier in classic.
The Cleric aggro issue on engages was due to a bad roll on the CH witness check and warriors not using click aggro on engage.
It definitely existed on Al'Kabor, and there is evidence about the tactic with bards using Group DA on bards.
While I do understand this would shake up the balance of the current meta, there are far more imbalanced things on P99 than this would be. The extreme use of clicky aggro and clicky instant CHs for example. Plenty of other Titanium client related things that also are imbalanced compared to the classic era like Cycle Target and scroll wheel to 3rd person.
https://m.youtube.com/watch?v=9opZFThy95w
This Cleric does a group CH on Sontalak and immediately DAs and clicks it off a little after. As a way to burn aggro.