The reason being is because people will just go for what kills the fastest, which is why shotguns dominated pvp for the whole of year 1. Another thing to add to it as well is what Bungie call a weapons balance is just a reverse of the numbers, first: Auto Rifles, dominated early pvp, Pulse's were non-existent and so were Scouts, Hand Cannons were slightly viable, then the Auto Rifle nerf came, Hand Cannons were buffed and the roles switched from dominant to dominated. Next Pulse's were buffed and Hand Cannons were nerfed, Role switched again, now Pulse's got nerfed Hand Cannons got a buff and Auto Rifles got a 0.04% buff ... so now Hand Cannons dominate. The only reason MIDA is so popular right now is because its just a great exotic gun, extremely balanced and a good all round exotic. What bungie calls a weapons balance is a simply a reverse of 1 of the 4 primaries, that switch from dominant to dominated, so there will always be a meta and people will always use only the hand full of guns out of that category that have the fastest time to kill. Its seriously sad as SO many weapons are left out, removing variety from the game, it won't be all that healthy to have EVERY weapon viable but it would be nice to have more than what Bungie are making the meta, its always only 1-5 guns that are viable, use anything else and unless your seriously skilled your going to be putting yourself at a disadvantage.