Disclaimer: My K/D is about 0.97 as of this post. I've never played a competitive FPS before Destiny, and I've only been in Crucible for a little over a week. I am experienced with competitive balance and meta games in general from both play and theory. I'm very serious about improving, but if you want to brush off what I say, feel free. Having experienced using Fusion rifles in the Thorn bounty, and generally theory crafting on how to improve my skills, I think it would productive to share what I've discovered about them. I find that they're best used as Defensive Weapons and suspect that they're vital to Destiny's metagame, so long as they're limited to that niche and not used as offensive weapons. Without FRs, I think the metagame would likely evolve into a Shotgun Rushfest; ARs simply don't have enough killing power to stop a player from rushing from Mid to CQC reliably, Scout Rifles would get no play, and Hand Cannons have too steep a learning curve to be a strong counter for all but the best players. A hardcore metagame would evolve, and while that sounds good on paper it's a death sentence to a community's growth. Newbies would get frustrated and quit before they can improve. I think the Devs have figured this out; that's why they haven't been nerfed. When I score a kill with a Fusion Rifle, it's usually because of one or more of the following: 1) My target wasn't using cover effectively, or there was no cover to be had. Fusion Rifles are meant to punish players who are not conscious of cover in a game with otherwise long TTK. 2) They attempted to rush me with a Shotgun from mid range. Again, this is exactly what they are meant to do for the metagame. 3) I flanked them or they were otherwise distracted. Any gun would do the same. I've also noticed the weakness of Fusion rifles while using them and fighting against them: 1) They're trash in CQC. If a Shotgun Run n' Gunner gets to halitosis range, it's too late to begin charging unless s/he messed up. 2) Missing is extremely punishing due to the charge time. 3) Using the weapon significantly reduces your effective mobility; sprinting and sliding offensively are off the table, and firing from mid-air has never worked for me. They are not conducive to a Run n' Gun style. 4) They make a very distinctive sound. This tips your hand to the enemy giving them time to prepare, and when you're used to them you get a feel for exactly when they're going to fire by the sound alone. Shooting from cover is the safest way to avoid eating hadrons. If that's not possible, jumping to the side just before a Fusion Rifle fires is an effective way to avoid death. If you're close enough, you can jump over their heads and rain buckshot on them from above. If you're really familiar with them, you can Slide right under their fire and kill them. The recoil will divert most of the shot above you, unless they were aiming for your legs. I've done it a few times, and nothing is more satisfying. Whatever you do, don't be an easy target; don't run in straight lines, and don't get greedy with your shots. Use grenades to reduce your Time to Kill. Lastly, your load-out can't answer every encounter. Know your strengths and capitalize on them. Accept your weakness, and avoid having them exploited.
First off, you've only played 151 games in Crucible. So regardless of your understanding of meta and competitive games, you lack the experience to really judge how well fusion rifles perform as a whole. I'm gonna do my best to invalidate every point you made without coming off as a douche. Using them in the Thorn bounty I'm assuming you're referring to the void kills in crucible. This isn't even almost enough to say that Fusions are best used Defensively. All you need is a FR with a medium high charge rate and good impact and you're beyond set to wreck face. Many people use FRs exclusively. This is because they have better range than shotguns, the ability to kill more often than snipers, and more ammo than either making them anytime weapons. Thinking that the entire game would devolve into shotgun rushdown is just a bit on the extreme side. Shotguns wouldn't have anymore dominance than they already do. Saying that ARs lack the power to compete is something only someone new to the game would say. Makes sense seeing how all the new ARs have extremely low impact. However, guns such as the Shingen E, Galahad, Shadowprice, and of course the Suros Regime that'll kill before you even realize you're being shot at. Scout rifles and handcannons are both precision based weapons capable of dropping a shotgunner from mid range so long as the user is accurate. Handcannons killing in 2 to 3 headshots, and scout rifles killing in 3- 5 depending on rate of fire. They would still be used by the players who actually think and don't want to eat shotguns all day. Knowing that so many people use them would cause players to use weapons to combat them, and nothing beats a shotgun quite like being out of range. I'm not quite sure about the matches you've been in, but I assure you that taking cover from a fusion rifle is rarely an option. If Destiny were a 1v1 game then sure, but in a 3v3 or 6v6 environment that isn't very likely or safe. Not to mention the person with the fusion rifle can just charge while chasing you. I can agree that fusion rifles are meant to shutdown rush players from mid range. What I can't agree with though is the hipfire accuracy and auto rifle range that many of them have. It's not fully true that any gun will kill you because you flank someone. I've been flanked and managed to dodge enough shots to win battles with my scout rifles or handcannons. You mentioned missing with fusion rifles which just doesn't happen under normal circumstances. They're accurate to hipfire and pinpoint when zoomed. The high impact ones can literally score a kill with only half of the bars hitting. The high stability ones can be used while airborne, and the high range ones will outshoot even ARs and some handcannons depending. You can CERTAINLY run and gun with a fusion rifle, just don't have one with really low stability and you're good. The sound doesn't even last long enough to let your opponent prepare sadly. Anyone who's good with a fusion rifle wont begin charging unless they know they're going to take someone out. So the sound doesn't help the combating player. I learned very early on that testing a fusion rifle is never a good idea. Especially with varying charge rates. You don't know how soon it'll go off. But it's faster than 3 shots from any scout rifle that's for sure. Jumping and strafing won't work on someone using Pocket Infinity or good reflexes. (or a person with 10 Sensitivity for that matter) Sliding won't work unless your opponent with the FR doesn't know how to look down. Jumping over them can be countered by sprinting forward 9 times out of 10. It's only going to really work if that person was devoted to getting off that shot.