Shadowstalker is very tanky. But leaving it alive is very risky as its Daydream (50% chance of success) + Dreamhunt can one-shot most Arks.
Let’s share how you counter it in PVP, here are what I do/what I have seen people doing:
(1) Knock it back. But you still have to deal with it at the end.
(2) Minespider’s time bomb. This is my current strategy.
(3) Mysticbane from Shisaguard. Forget about it, it is too weak, only hits ~300.
(4) Plasmorex’s Acid body. I have been seeing people doing this, putting a Plasmorex to bait Shadowstalker’s Chain claw, which will lower Shadowstalker’s defence and resist significantly, making it much easier to kill. But the disadvantage is that you loss 1 Ark. Maybe Arks with Decay will be better?
(5) Stun and then Timestrike, won’t one-shot Shadowstalker, but can still deal significant damage.