You have two different Halberds, and each is treated individually, me thinks. If you had ONE mega Halberd, we'll call it a Guisarme-Guisarme-Awl-Pike-Fauchard, then I think you could call it 4 damage. As it stands, I think it's:
Number of Halberds * {Number of rooms * [(2 damage) - (1 * active shields)]}
Then Rockmen's damage resistance if/then statements and then a whole 'negative results = 0' statement somewhere....
Either way, the Halberd is my weapon of choice. I have tried to move away from any dependence on missiles because the cost of upkeep (ammunition) is just too much and depends on regular visits to stores. I am bouncing between 1 mega-ion cannon and the Halberd as a baseline, with any other weapons as gravy, OR a crap ton of multiple fire lasers with the Halberd once the shields are dropped - I'm leaning towards liking the latter a bit more.
I've also explored teleporting crew to wreak havoc, and I like it! I think it distracts the crew enough so they don't repair their shield/weapon systems fast enough and lets me continue to rain down hell. Just don't get the bright idea of teleporting your crew to a drone, because I discovered AFTER the fact that the drones don't use O2 and my crew can't hold their breath long enough for the teleporters to recharge and bring them home...
PS I had to teach Chrome that 'teleporters', 'fauchard', and 'guisarme' are words. I thought that Google had enough nerd-cred to bake those right into the spell-checker, but I guess not. Jocks.