Yeah .. especially since Pulse Beam Rifle doesn't trigger Killer Instinct at all, Overdrive is so much better
for that kind of build. I went DEX / CON / REC for superstats btw. so i have also enough energy for
Orbital Cannon even without cost discount items, and i use Form of the Tempest, since i don't have
much INT, and i tried an EGO Build on the PTS but not really liked that more.

I think you need to test things out in the Powehouse. I was very surprised to find Assault Rifle Rank 2 with Mow Em Down to be clearly superior to Rank 3. (And better than Gatling Gun Rank 3.) You just can't figure these things out on paper sometimes.

Try it vs. other ST attacks you are thinking of on a level 40 dummy and see which one kills the dummy the fastest. For a timer, I just activate a passive defense. If you think you will wind up short on energy, I temporarily take Circle of Arcane Power Rank 3. Make sure you have 8 stacks on Concentration for all tests.

P.S. I also like being able to move around while using Assault Rifle (vs. Gatling Gun for example.)