There is no dedicated healer, tank or DPS. instead all classes can heal themselves to some extent, all classes can DPS, and although not everyone can tank, everyone can dodge and has abilities to reduce dmg done to them.
Depending on weapon, utlity skills and traits though you can focus on different things. So you could build your class more on pure DPS, or a condition build where you focus on keeping your enemy fully debuffed and stack dots, or you could have a support build that is viable for several classes that can heal others and remove negative conditions from your allies.
So if you still want to play a healer/support type setup you can, but you can just change your weapons and traits and you could now be in a DPS setup

(unlike some games where a healer class trying to play DPS just isn't viable, in gw2 pretty much all classes have multiple options).