I don't foresee this having any practical use in upcoming (or existing) raids, trials and probably even dungeons. Repose (or Sleep in general) has only really been "effective" in content like Eureka or PoTD/HoH where a common factor is actually avoiding enemies or only being able to handle one particularly lethal enemy at a time. If the devs for whatever reason decide to allow a trial or raid boss (or even adds) to be susceptible to sleep, then cool, I guess? But the devs always seemed really averse to players having the potential to "cheese" endgame mechanics with CC- largely a reason why BLU is the proverbial black sheep.

If you ask me, all Healers getting Repose seems more like a byproduct of their healer homogenization so when it comes to needing CC in places like Eureka 2.0/PotD/HOH, no single healer is better equipped to handle that type of situation when things start to go south.