Hi, hi! Backline weapons enjoyer with a Tri-Stringer pocket here, I agree with pretty much everything here, but also wanna add a thing.
Since the Tri-Stringer is a backline, there'll be situations where most of your teammates are down and you need to give them jumps. On some maps where the enemies can approach you from multiple angles, say Undertow Spillway or Sturgeon Shipyard, you can use Mist as a way to "guard" one path while focusing on the other path with your main.
You do still need to keep an eye on that path, since Mist doesn't really stop anyone on it's own. But it does discourage/slow down pushes from that direction. That can often be just enough to get your frontlines in or to get you out.
Most important thing really is that Mist can be your second pair of eyes. Use it to passively keep tabs on a path while you focus on another. Really learn to recognise the sound the mist makes when an enemy is being affected by it. But dont worry about having it up all the time, the main is still the star of the show here.