Remember the caveat emptor that the PTR is the PTR and things are subject to change but we always look to the PTR for early indications of what we might want to get ready for with the next patch. Best case scenario the next patch is still a few months away so you have time to work on things. But that also leaves the door open for change on the PTR. With that said, lets move to the topic at hand.
Note: If they change it that the dwarven bunker /war mill can give you ship fleet upgrades than please disregard this post, forget you were ever here. This post is written with the idea that the bunker / mill will continue to only give follower upgrades.
We have been told that the maximum follower item level will remain at 675 in 6.2 from this twitter post.
With that said it is time I change my suggestion that people have the dwarven bunker / war mill in their garrison. This was one of the two main buildings for getting follower upgrades. Between this and the salvage yard giving follower upgrades I would hazard a guess that most people are somewhere in a position like I am at the moment with multiple stacks of follower upgrades and 40 followers or more sitting at 675 item level.
If we are not going to be getting any new followers and the follower item level is not going to be increased, the value of the dwarven bunker / war mill has greatly decreased. Unless you are still collecting the pieces to buy for transmog or really really like getting a free coin to roll with, and we do not know yet if it will give the new coin so beware, there really is no reason to have the dwarven bunker any longer. If, and only if, the dwarven bunker / war mill does not give the new coin than its value is basically nil.
So I suggest it is time to ditch the dwarven bunker / war mill. The only reasons I can currently see to keep it is if you are still trying to collect the transmog gear or if you are a new, or newish, 100 and still want to gear up your followers.
Remember, the old follower missions will remain which means there will still be highmaul missions and blackrock foundry missions which could serve as a nice way to gear up an alt, albeit slowly and requiring luck, but a solid way none the less. Not to mention doing missions for gold will always be nice and higher geared followers means better missions and more success at them.
Outside of those reasons it is now time to take a look at what other level three buildings there are out there that could be an option.
If everyone read my guides here from the beta and took my suggestions I am going to guess you all have the barracks. If you do not then that is worth considering. The barracks allows you to have 25 active followers which means you can send more out on missions. This means more treasure hunters to make you gold, more scavengers to make gather you resources, more people to get you salvage boxes or other goodies that you can sell. So the barracks is the best option to replace your dwarven bunker / wall mill if you did not already have one.
The stables would be my choice for the small increased mount speed, the protection from being stunned or dismount while riding and the bonus that you can interact with items while remaining mounted.
If you happen to be a gather this ability is priceless in my opinion. For the time I had the stables while I was collecting the 8 free mounts, 6 from quests and 2 from achievements, this was my favorite feature as an herbalist. I always stopped to gather every time being I did not get dismounted but since I replaced the stables with the bunker I have not stopped to gather a single herb in the world, not worth stopping if I am going to get dismounted. So this is the leading candidate to be my second large building. I like being able to interact with items while mounted.
But do not discount the mage tower / spirit lodge. It sure has its uses. In the past patch they added work orders to the tower / lodge so that you can get mission rush orders from it. This is great for completing missions faster. Getting the gear missions done instantly, getting that gold faster, getting your treasure hunters on one missions, finishing it, putting them on another, finishing it, etc over and over. That way you can end up getting the maximum effect from your followers.
Add that nice little bonus recently added to the tower / lodge that was not a part of its original release and the portals you can have all over draenor and you might just have a winner of a choice here. I have the tower on my tank and I have ports to nargand which was right near the highmual raid and to gorgrond which was right near the blackrock foundry raid so hoping that they keep up with what seems to be the idea we might see them adding a port to tanaan that is right near the new raid.
There is also another beautiful thing with those portals if you happen to be the raid leader. If you have a portal to the area right near the raid, people can visit your garrison and use your portal to get to the raid faster. A great little bonus for groups without a lock or even for groups with them, so the lock can get there faster. So the mage tower / spirit lodge is not only a very viable replacement for the bunker / mill but it might be the best one for you.
The last large building that remains is exactly as it was when I first described it, a complete waste of time. You can build the gearworks if you wish, it will give you many fun toys that you can use out and about in the world and who does not love having a robot chicken fight with you or a rocket pack so you can "sort of" fly around draenor some. But outside of the "fun" factor the gearworks holds absolutely no practical purpose like the stables or the tower / lodge do as a replacement for the bunker.
Do you think it is time to ditch the bunker / mill? I sure do and it is my suggestion that people do so.
I will most likely be going with the stables on gathering characters and the tower / lodge with non gathering characters. A simple either or decision for me as those are the only two options I see now for a second large building, of course with the barracks staying our first.