Druid: Self Healing
Druid has very strong burst healing, but sustain only really comes from Regen and some staff skills. However, that being said you will definitely be losing damage by picking up staff and taking the druid line versus another weapon on base ranger.
The outgoing healing is also bolstered by a lot more incoming healing, so Druid has much more sustain if he/she can generate AF. If he/she cannot generate enough AF to reliably enter CAF, then the sustain is little more than standard Ranger, possibly even less actually depending on trait and weapon choices, if you take evasion into account.
Sustain is good with TU/Rejuvenating Tides. Currently if you cast Rejuvenating Tides and then leave Avatar Form, it continues to heal you(water field also remains). Essentially you can get~15s of 800hps by combining these two skills. What’s more is that if you use Grace of the Land, the stacks build with the Rejuvenating Tides even after you have left the form. So you can pop in, cast skill 4, and then leave immediately getting the sustained heals and the damage buff at the same time.