I can see what you're trying to say, but I don't think it will be a match changer like you're thinking it will be. Before the special ammo nerf, yes I totally agree with you. After the nerf? It's become harder to exploit and depend on that. If there were no revives, that changes everything and it would be super OP. But with revives, it makes it a little better. I do believe we will see a lot more sniping in the trials and less aggressive play.
If it was "Game Breaking" they would have fixed it by now. It is nowhere near game breaking, especially with the special ammo nerf. Fusion and Shottys broke the game far more than final round on a sniper. If it was so game breaking, there would be much more complaints about it, but for crucible, it's been Fusions OP, Blink Shotty OP, Suros OP, and Hand Cannons OP. When's the last time you said, man this whole team using final round snipers?
It also matters that margin of error is far less with 1-2 final round bullets that you start off with if you're simply going for a final round exploit. That's what I was trying to say before. You have the potential for 2-3 final round kills in your clip, but if you miss, you're a sitting duck as you have to reload or switch weapons then try to fight an oncoming opponent. And you've exhausted your whole clip at that point. Having the 6-7 Sniper bullets is far more valuable than 2-3 bullets in your sniper round.