Not nearly as fast as other competitive multiplayer games. But, the point is not that the tkk in Destiny is too slow in and of itself, the issue is player movement speed. The fact that all classes, but especially titans, are able to close a large gap before a primary weapon can kill them is what is making shotguns dominant. The typical scenario isn't two people standing off at mid-range landing 3 headshots on each other. It's usually rounding corners and the person with the shotgun will duck to cover and regen shield then charge/blink in or skate/garrison dodge with juggernaut which is difficult to counter under typical scenarios. Reducing player movement speed would be game breaking. The best solution would be to revamp all weapons to have a very similar ttk at their appropriate ranges in pvp and that ttk needs to be quicker. Destiny pvp is fast paced in every aspect except for primary weapons.