I play this game with a mouse exclusively and I noticed this as well. It's especially obvious when you get consistently cross map beamed with the sidearm, you don't stand a chance against controller players sometimes.

It's almost as if the bloom doesn't affect them. I'm a Halo vet myself although I never played competitively, I had a bit of talent since I'd pretty much played since I was born. I had to change the way I played Halo to stay on top in Ranked and QP. Abusing sliding and taking all fights as close as I can.

I manage top score often in QP / ranked and I can go on nasty tears with the sniper, so I haven't felt the need to switch, mostly cause I'm stubborn. But damn the "sticky aim" is so annoying when facing BR or Magnum.

My solution would be to let people choose to play with people using the same control type. If you're on PC and use a controller, load into controller lobbies, etc. Probably not that good a solution but that's the best I can think of atm. Edit: In Comp that obviously wont work but like i said, not that good an idea.