Quite honestly I'm of the opinion the M48 GAU is a ridiculously OP gamebreaking piece of crap...along with the T-15.
It really is a fun-killer when you're teamed with them. Think about it: does anybody log in just to be a spectator? Which is pretty much what you are if you try to play an MBT.
I speak as someone who regularly gets teams full of autocannon and missile spammers.
I wouldn't go so far as to openly call someone a selfish prick for playing them, but if there is more than one OP gamebreaker in the team I simply quit t he battle before it starts and move on to the next.
Needless to say I do quit quite a lot of battles (90% of the time they do just fine without me). Its just ridiculous how often the matchmaker puts PAIRS of these things in my teams.
As if the game weren't already broken enough, the devs now seem determined to fill every tier with these shitty pew-pew / blam-blam vehicles.