The trick to beating shotgun noobs is the throwing knife. Spec so you have 2 and you get your cooldown reset when you get a precision kill with it, put 2-3 shots into them with the Suros Regime to get their shields down to below half when you see them charging at you in a straight line, and then put a throwing knife in their face. Instant kill and you get your cooldown back before they ever get in range to kill you. Works wonders for striker titans also. You will literally always have it up once you learn how to aim it consistently to hit them in the face from range. Its the most overpowered, under appreciated part of being a hunter in PvP. It makes Gunslinger better than Bladedancer in PvP before you ever even factor in Golden Gun, which is no joke either.
As for the fusion rifle, you basically just have to dance around and keep your reticle on their head and take them down before they get that second shot off. If they're good, they won't miss more than once, and sometimes you just have to accept you got zapped by a decent player. It happens. Like I said, I just cracked the top 5% and that's with a 1.8 lifetime K/D ratio. Since I got the Suros and the Knucklehead Radar maxed out its probably improved to around 2.0, but that's still a lot of deaths in a game. Its easy to die with all the supers, rockets, shotguns, fusion rifles, etc. You can play a good game and still be only around a 1.5 at the end. Its not Call of Duty where 1.5 is mediocre.
30 and 10 is a hell of a game. Next time I'm on and you're playing add me, we'll cause more damage together than by ourselves.