Garrisons are still useful if you've invested a little time in them. They removed the Treasure Hunter trait from followers and the gold missions, but replace TH with a bigger garrison resources buff. They upped the price of the tradeskill stuff on the special vendors, but that's offset by the GR follower buff.
People still buy the WoD tradeskill materials because they're easy to use for leveling up trades and less expensive. You can make some decent gold.
The Inn/Tavern produces some toys that are easy to acquire with a high level character because you can solo the dungeon missions in no time. There's a toy that actually works as a mini-flask buff that gives all stats like +50 for an hour. I use it for heroics or easy m0's that don't need real flasks. If you're a Dark Souls fan, there's a follower there that's a knockoff of Solaire, and if you interact with him in your garrison, you can get a bonfire toy.
Some of the buildings are mainly fluff, like the stables for mounts.
The pet menagerie is relatively useful for collectors and battlers, since it provides items and an easy way to level them up.
The tradeskill huts are still useful for little odds and ends.
The alchemist hut can produce WoD flasks if you provide ingredients, which are useful for low level mythics, heroics, or even helping with leveling your alts. If you equip it with a follower, they provide a daily quest for stat potions. The alchemical catalysts you can make there can sell well sometimes on the auction house.
The engineering hut can produce gliders if you provide it with (I think) sumptuous fur and ore.
The inscription hut can make those tarot cards you can click that have random gold rewards. Sometimes you get big ones, but you have to click through a bunch of them sometimes.
The tailoring hut can provide a lot of hexweave cloth, which you can use to make hexweave bags. The hut doesn't do it, so you need an actual tailor and the hexweave cloth is soulbound, so keep that in mind.
The bank is awesome because its your own bank, guild bank, and has transmog services.
If you're looking to start building your garrison, get the treasure hunting mods out there that show where a lot of the resources are in Draenor. The salvage yard and war mill are useful for gearing up followers, try to get the Inn up too. The trading post is super useful and costs no resources, only gold, so get that going quick.
There's a lot of followers you can pick up super quick to fill out your roster, but make sure to use the Inn every week and start filtering some of them out. Any of the bodyguards need to be weeded out when you're maxed on followers, because their Bodyguard trait can't be replaced. So you have 1 out of 3 traits that are completely useless for missions. The dancer, hearthstone, and ogre buddy trait buffs are great and best used for overwriting some followers' tradeskills. If you do use a "reroll" book, keep in mind that any follower that you recruited with a tradeskill as a default, will reroll with that tradeskill every time. So say you got Ahm, who has enchanting. If you overwrote it with ogre buddy, then later want to reroll his traits, he'll get some random ones, but he'll get Enchanting back as one of them. So be wary of that.
I know this was kind of overboard, but hopefully anyone fucking with garrisons has a good heads up now. I still use them personally, but not as heavily as before. The conveniences of them without the long ass load times and clusterfuck of Dalaran makes me happy. Being able to use a flying mount there is an added bonus.