It's visual glitch as it used to be on Gunner (still is), just for all classes now and reported it.
Note: when ppl report stuff, should include screenshot or video in it because I need to go in the game anyways and record it (if i'm lucky enough to find it). Videos/screenshots are helpful for devs and finding issue in code would be easier.
U probably think on bug as this one is, just on Tank.
To make it less confusing for players: It displays wrong weapon (check killfeed and more experienced players would be able to make a difference between HMG and mauler dmg), currently exists on Gunner, Scout, Tank, Tech, Shocker, Blaster, Blazer. Player most likely see all normal on his screen, but it's not like that for other players in the match.
Main issue for me was how it is really hard to say which weapon some player is using, is it long or short ranged and was really confused few times. Blazer was using heat ray on my screen while in reality he used flamethrower and that was just painful.