Druid or Revenant
Druid brings CC, party DPS support, and burst healing, at the cost of some personal DPS and survivability. You can use base Ranger traits to improve Spirits (which provide unique buffs) to apply pulsing boons. Revenant brings DPS (Shiro), boon manipulation (Mallyx), party boons (Glint), sustained healing (Ventari), and damage mitigation/support (Jalis).