Lot's of good information in this thread.
So I missed the entire WoD expansion and from what I've been reading over the year(s), sort of glad I did. So a few questions:
1. Is it even worth my time to get Draenor flying? They should allow you to buy it with gold at this point.
2. Garrisons. What the fuck is the point now? I boosted my druid to 100 and went into it for the first time and looks like a bunch of shit is at Tier 2.
3. Usually played tanks in the past, but want to try healer. Would you prefer a monk or druid in your party? I honestly like aspects of each class so it's a tough call.
Forget anything about Draenor, it's in the past and completely irrelevant. This includes garrisons.
Restodruid and Mistweaver are both great healers, with druid requiring a little bit of setup with multiple hots rolling and monk being more direct and having very good healing spells (you'll love Vivify). Druids have it slightly worse with mana, because monks can work their asses off to gain a bunch back, but the difference is not astounding.
Druids have the best tank cooldown in game (because it can be used more often) and a good group/raid heal which is Tranquillity. One of the artifact golden traits allows to cast it on the move and boosts it by 20%, but it's still channeled. Monks Revival is still extremely powerful, because it's an instant healing bomb (with a dispel included) and a golden trait adds a 30% HoT to it.
Both classes can cast for zero mana cost for 10 seconds, but the monk must talent into it and the druid could theoretically cast it on someone else.
Mobility: monks win, Roll/Chi Torpedo is just the best, but druids can talent Displacer Beast which is a Blink type skill (but it puts you in cat form, so you have to shift out of it) and can talent Feral Affinity for a permanent 15% movement speed boost.
DPSing while healing: monk can use Crackling Jade Lightning (channeled) or go melee, which does more damage, allows to do AoE dps, while druids use essentially Moonfire, Sunfire and Wrath, or they can talent into Balance or Feral Affinities for extra skills.
Artifact power active skill: the Monk one can push astoundingly big single target heals if the fight is long enough (really big), the druid one shines when a lot of people have hots, the more the merrier, so it's extremely good in raids, but good also in groups.
If you are planning to do a ton of Mythic dungeons, Druid is maybe a bit better for the tank cooldown, which can be used much more often.
I like both, I'll certainly play both sooner or later.