Mastering Downed State In PvP

Introduction

A PvP guide to stomping downed enemies in PvP as well as how to survive stomp attempts on each profession.

These are tips for dealing with downed enemies based on their profession.

There's not much you can do here, their Vapor Form allows them to go invulnerable and travel around for a few seconds. They get to avoid any stomp attempts. Best advice is to start cleaving or stomping as soon as possible to quickly force out the Vapor Form, after that they're a free kill.

They have not one but 2 downed CC skills. The first one which is instantly available is a ranged pull called Grappling Line. Their character pulls their right hand back as they charge up the skill, that's your sign to dodge if you can't negate the attack.
The second one becomes available after a few seconds in downed state, Booby Trap is an AoE knockback. Animation: they raise their right hand towards the sky.
Stability works on both and so does Blind (if your timing is good) or invulnerabilities like Mist Form. Grappling Line could also be shut down with Swirling Winds or any other anti-projectile skill. If you don't waste any time then they don't get to use their Booby Trap, but if they do then the projectile denial won't be enough.
Double teleports could work but Grappling Line is ranged so there's a chance they could snipe you and interrupt the cast.
Stealth might work on Grappling Line but not Booby Trap, and even with Grappling Line you should be behind the target to avoid them getting lucky with a random Grappling they throw forward.

Downed AoE CC skill Wave of Light is available to them right away. Animation: they raise their right hand towards the sky.
Stability and invulnerabilities are a safe bet.
Blind and double teleports work with proper timing.
Their downed skill #3 is an AoE rez with multiple pulses. Not a major threat on its own but could make it easier for their allies to pick them up, and stomping them while they have high enough downed HP could give them enough time to self-rez.

Mesmers have a teleport skill that gives them Stealth and summons a clone.
The clone appears before they leave stealth, so always stomp the Mesmer that appears second - they're the real one.
This one's a bit tricky but if you have an instant teleport skill that's either ground targeted or takes you right to the target like Steal then with proper timing you could stomp them.
To efficiently stomp a Mesmer you must begin stomping, interrupt your own cast about halfway through by sidestepping then start stomping again. With a little luck they fell for your first attempt and used their Deception right as you begin the second stomp. Deception's stealth duration is 2 seconds, stomping takes 3, you'll have a little less then 1 second to locate the downed Mesmer coming out of stealth and teleport close enough that your stomp connects. You mustn't move during the second stomp!
Honestly just cleave them, this isn't worth it but hey, if you like a challenge you could try.
Be careful with their downed skill #3, Phantasmal Rogue hits like a truck. If you're below ~7k HP you should definitely dodge this Phantasm just to be safe.

Their downed CC isn't very dangerous, long cast time and obvious animation (black symbol above their head, raised right arm).
Easy to stomp with Stability, Blind, Stealth and invulnerabilities like.
Blind and double teleports work with proper timing.