There are a few pretty much instakill abilities in the game that you need to dodge or you will go down instantly (if you haven't specced for full toughness + vitality then you might live with 2-4k health, not long though):
- Warrior's Hundred Blades, need to dodge or be killed from 100% to (close to depending on spec) 0% in one move. Has 8 seconds cooldown.
- Thieves' Pistol Whip: need to use stun breaker and dodge or be instagibbed with 1 or 2 whips. No cooldown obviously.
- Mesmers' Blurred Frenzy (to a much lesser extend) does a whole lot of damage if you don't dodge, plus makes the mesmer invulnerable. This is the least of the instagib evils, but it bears mentioning because it too has a low 10 seconds cooldown.
The "defense" of players playing those classes is always "you need to dodge this and that move you noob".
But how come those instakill moves have such low (or none) cooldown? To regenerate enough endurance for 1 dodge you need 10 seconds. Which means you will not be able to dodge every 100blades if the warrior uses it on cooldown.
Warriors also have bolas (20 seconds) and bulls charge (40 seconds) to immobilize/knockdown you, you you will need to use a long utility skill if you have one to break the CC and get away from the instakill. Same for pistol whip which stuns you.
How is it fair that those "dodge/break stun or die" moves have less than 10 seconds cooldown? When you need 10 seconds to regenerate a single dodge? And stunbreaker utilities usually have 40-60 seconds cooldown?
Seriously, 100b is just a ridiculously stupid skill that is worthless without a CC. You can just walk away from it. It will do damage, but not to the full extent. If you walk away without dodging, it does the same damage as any other major damage skill in the game.
If you get CC'd, you should have a stun breaker. And the warrior CC skills have significant cooldown.
Pistol whip can be annoying, and takes a few hits to kill you. It's not instant death. A glass cannon thief will run away the moment you break stun and dodge away. Most thiefs wont give up on you, they will keep their hit and run tactics. You need to have something prepared for them, like a blind, etc. And the haste utility has a significant cooldown.
Tourney games rarely play out as you describe them. If there would be a truly OP class, everyone would roll those in tourney. But actually there is none, or the broken builds have not been discovered yet.
I played in tourneys against burst teams, like 5 people chain CCing every target and bursting them down in 3-4 seconds tops. Still, you can just outplay them by split tactics. Conquest mode is actually put in place to make it possible to counter such 5 man burst builds not by force, but with brains.
Bottom line is, not glass cannon build can burst you down with one combo 1v1 if you are prepared (like not 20% hp, out of endurance, no heal and utilities on cooldown). And after their combo they are pretty much at your mercy.
I wont use the l2p cliche, since it rude and only shows how limited people are. Instead I'll say that you need to practice, ask friends or on the forums about the strength and weaknesses of certain builds. Make use of your builds strength.