This sounds like a complete recipe for disaster. Slower pacing in this case doesn’t mean lower TTK and in fact messages about the complete opposite where heroes explode so fast that teams are forced to play slower simply to not die. From the role passives and the change in team formats it was already obvious that offensive strats will most likely evolve into more flanker based gameplay (which is worse) and defense will most likely evolve into hit-scan bunkering (which is worse) where supports will in teamfights pace themselves around their bursty abilities to have slight windows of opportunity against the DPS while tanks are there to offer momentary small area denial
If this is how the PvP starts to go, then the PvP side of the game will absolutely die. This sounds like a complete nightmare to even consider playing
I sincerely hope that there will be a “OW Classic” option for 6v6 formats somewhere in the game where we can actually keep playing proper OW if it turns out that the matches evolve into short teamfight bursts with deathmatch elements being the core gameplay