While most healers have less CDs defensively, Druids are still lacking in quite a few I'd argue. Paladins for example have DP and DS (I don't count any externals, they're intended to be external). They're also one of two non-tank specs to have bonus health (the other being Fury Warrior) because they use health as a resource.
Shamans are the only other class that I immediately can think of with lackluster defensives while all other classes have at least 2 self-healing/defensive capabilities. Barkskin is very lackluster (20% is weak as hell) and Bear Form/FR is being nerfed greatly in BfA. At the very least, Shamans have Reincarnate.
As in a Guardian Druid shifting out of form, sorry if I wasn't clear. No other tank has that insane handicap on their utility spells. Paladins/Monks have vulnerabilities if they're in the middle of casting a cast-time spell (Flash of Light/Effuse), but that only means all attacks will hit them. Guardians shifting out of form means they just get oneshot by a melee swing. Sure you normally shouldn't be shifting out of form but again, it cuts your utility down greatly while, again, no other tank has that consequence. Only Druids have this problem with forms/stances while all other classes have had their removed. Even Shadow Priest, still having a form, instead got Shadow/Disc versions of spells that would break their form.
Does that make HPal unique because they rely exclusively on non-HoTs and can sacrifice some health to do some things? Not really.
I'm just saying this doesn't make them unique. Both Shamans and Monks have a slew of HoTs.
Shamans for example: Riptide, Healing Rain, HST, HTT, Spirit Link (technically a HoT), I'm sure I'm missing a few. Monks I don't remember their spells but a majority of their spells are also HoTs. Again, don't see how Druids are unique to this. Just because they rely more on HoTs than other classes (while TBH I think Monk has them tied), doesn't make them unique.
As for the Shapeshifting, the only real benefit besides Travel Form is shifting to remove roots/snares, which yes is a great benefit, but the cost of it can be really shitty, especially in PvE. Again as I said above, name me one other class who loses around half their utility spells because they have to change stance/shift out of form (ON LIVE/BfA, not talking about expansions prior to Legion). Name me one other tank who is put in grave danger for any niche scenario because they had to use a specific spell/utility from their toolkit?