It indeed is button bloating.

You don't need AoE variant, just makes them AoE per default nothing will change.
WAR primal rend is an AoE but works wonderfully against a single target.

The Overheat starter being the first GCD of the Overheat phase, it should give 4 stacks of Overheat.
Giving it 5 stacks will simply make Overheat phase longer and reduce the MCH flexibility.

As for the finisher, you can even turn Scatter gun into a superior version during Overheat, let's say "Super shotgun".
Straight line AoE, makes Scattergun button relevant in single target situations.