Support weapons as designed by devs and gamers are usually crap. Why would I use a 'support' weapon, when I can just use a REAL weapon and do the same "support" but this time actually kill something? I've always hated how people view "support" weapons as if they're supposed to be peashooter garbage. CAS is a proper support weapon. OB's are proper support weapons. Mortars are proper support weapons.
Guns that you might as well be running up and knifing the xeno instead of shooting are not "support" weapons, they are CRAP weapons.
Luckily the mouse isn't a crap weapon, it just mediocre. It can still be an ACTUAL support weapon and not useless crap or just mediocre, if it gets a little help to fill a desperately needed weapon role for marines - longer range burst damage - but it's so clunky to use and easy to fuck up with, that nobody touches it.
I think if you just gave it IFF with fewer kits being available you'd solve 90% of the problem with this gun.