Hi, AmmoChain has recently been modified to address some of the overpoweredness. Given the current trait requirements, MAC is no longer an extremely fast-firing ammo-less attack of pure carnage.
While MAC is indeed very strong in the past given that Finx2 and WK are requirements (making that A2 plasma rifle pure pwnage), the requirements of Relx2 now instead has made this über combination a little more delayed (at least clev 10 instead of clev 5).
It will be interesting to hear your views on where you had used MAC (e.g. difficulty levels, specific challenges), since under different circumstances, MAC may prove to be ridiculously overpowered, but in some others, it might just be barely enough.