Took this build and fixed it (Focus energy makes you not need to wait between heavy attacks without running Zenuric): https://overframe.gg/build/11721/fragor-prime/grasshopper-heavy-slam-nuke/
For 1 more forma you can prime the PP or for 2 you can [Sacrifice] it without an umbral forma :)
I try to make (relatively) good low forma builds that I personally use (or would if I had the forma/mods)