If you start a strike, heroic or regular, you get matched into a team. And being a team means working together, not repeatedly trying to run past all the enemies while the other two work their way through them, and dying, leaving the other two to kill all the enemies while you wait to respawn
Seriously, i've had 5 strikes today where someone kept trying the "mad dash" tactic. If you're there at the start of the strike, you shouldn't be ending it with less than 30 kills while i've got over 170
(Edit: the point i'm trying to say here is pull your weight, and work with your team. Don't be some idiot that runs off by themselves, dies without even reaching the next checkpoint, waits to revive, and then repeats that process multiple times in a single strike. It's basically the equivalent of sitting in the back doing a dance emote while the other 2 players are killing their way through
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Shooting your way through a strike, if you're competent and the team doesn't wipe, is 10-12 minutes. I always do most of the fights and it's consistent. Only times it's longer is when someone decides we can jump around to skip parts of the infinite forests in Glass or Grounded modifiers. Then you get stuck with a millions adds to kill by yourself. Then it's 15-20 minutes. Speedrunners have the impression they're going faster. Unless you're so good at it that you finish strikes in 8-10 minutes, you're not going any faster.