Do what you want to improve.

If you like optimizing defensive cooldowns, party-wide positioning, and enjoy thinking on a more strategic level then play a tank.

If you like the biggest numbers and want to find all of the ways to cheat death to make those numbers as big as they can possibly get then play dps.

If you don't want to take either path you don't want to be a dps or a tank. That doesn't mean you should play a healer.

If you don't want to improve, you don't want to play.