Guild Wars 2

So we all know that when you disengage from combat you regain full health in the matter of seconds
But how can thief disengage from combat (fighting me) using stealth so he regains full health in the matter of seconds and I am not disengaged from combat ???
This is clearly a BUG
When there are only 2 players fighting one gets disengaged from combat it should disengage also the other player IMMEDIATELY
Why thieves are going full damage zerker ? Because they have access to the best healing ability (exploit) in the game which allows them fully regain health in a matter of seconds
No other class can do that

They don’t disengage from combat, they use their heal skill, which on a glass canon with a tiny health pool, heals them back up to full.