It's going to be dope in PvP (if my pr dictions are true, based off the current way players interact with Pokémon).
In the main series, it was advantageous in PvP to switch out Pokémon and put in a counter (i.e. If your opponent swaps out their venusaur for their blastoise when your ccharizard is out, then swap in your venusaur!).
So, rock blast may be (theoretically) advantageous over stone edge, as it only requires golem to be exposed for a third of the time (1/3 energy cost of stone edge), thereby reducing the amount of time where an opponent may swap out their Pokémon for a grass or water type, and allowing golem to fire off a rock blast faster (1/2 damage, but compared to the potential damage they would take from a double weakness attack, it would be advantageous).
These are based off assumptions. Having a similar cooldown as stone edge, dealing 1/2 the damage but requiring 1/3 the energy cost makes it nearly equal, in MY opinion. I just obtained a RT/RB a couple of hours ago and I'm excited to try it out. In terms of the current gym mechanics, there are battles where golem KO's a Pokémon JUST before it has enough energy to fire off a stone edge (wasted energy). With rock blast, the problem of wasted energy isn't nearly as problematic
