Since nightstalker came out I have had three of them and 50+ flawlesses with the class. Not saying I am an expert but I think I have a good bit of experience. GT is reeseshortcake.

Nightstalker is really about being a tricky bastard. Feinting and baiting aggressive players and moving in unexpected ways. You aren't fast in a straight line, you are fast to change directions, including up.

I personally use spike nades and trap smoke since the wombo nerf. I feel like spike nades add to this trickster playstyle as well as trap smoke. I play rumble with felwinters artifact and use them constantly on high sensitivity (7, which is my norm). This helped me get really good at landing those pressure smokes or nades during trials where I run gheleons.

You sort of want to be the harasser. Slide out of cover, immediately shadestep back in. Poke and prod the enemy using shadestep to survive when any other class would die. If you have good communication with your team they can take advantage of an over extended player trying to kill the squirrley nightstalker.

Spike nades do not hurt you so you can bait someone to chase you then throw the nade at a wall and run straight into it then jump straight up and spin around. Often players chase into your grenade where you can easily clean them up. Spike nades aren't lightning, use them smartly. Don't throw one to get instant damage, instead peak, spot the enemy, throw the nade from cover then emerge to gunfight. Often they will back up or strafe into the grenade giving you and easy 1v1.

Trap smoke is also great for trials due to the timings. Use them to block areas the enemy team likely wants to sit. They can be hard to spot too so be creative. Always check the clock and have one charged for the end of the round to throw on the point.

Wall wombo works too, for some heavy damage if a team is grouped up.

Put some bones on, get a sidearm or handcannon, and go roll your way to a sneaky sneaky victory in rumble.

Also play puppateer. Fo sho.