Arcane Mages can barely touch WoW Forever's Dalaran dungeon, and Blizzard says that's the point
Those immune enemies are not a bug, and Mages will not be the only class that runs into one.
If you plan on playing or taking an Arcane Mage into City of Dalaran in WoW Forever, you should probably bring a backup plan.
On the latest episode of the official WoW Forever Podcast, Blizzard's encounter designers explained that a lot of the dungeon's enemies shrug off arcane damage. That is intended, and it is how new dungeons will work going forward.
Testers Could Not Hit Anything
The topic came up during a moment where the team talked about building City of Dalaran. Some testers went through it as Arcane Mages and came back with a complaint about how they could not hit anything. Well, the simple answer is that the place is full of arcane creatures, so yes, that is going to happen.
According to the devs, Dalaran was the first time their stance on immunities got properly tested. The rule itself is easy to follow; Creatures should behave the way you would expect them to. A robot should not bleed. A big arcane elemental probably should not care about arcane damage. The team said it felt obvious at the start and turned out to be a lot more complicated once players got involved.
Mages Are Not Locked Out
If you play Mage, there is no need to reroll. The devs were clear that you are not shut out of the dungeon. Even at that level, and even in Arcane spec, Mages have other tools to get through. You will just have to make more use of them instead of your usual buttons.
City of Dalaran is accessible between Levels 28 to 33, which fits right under the beta's Level 30 cap, so you can check how your own class handles it.
Every Class Gets Its "Rough Dungeon"
This is not a one-off for Mages either! The team mentioned Excavation Site in the Wetlands, which you can already run on the beta. If your group has no way to remove diseases or handle bleeds in there, you will feel it fast. Dalaran pushes that idea a step further, and the devs said future dungeons will keep doing the same.
The good news is that it will not always be the same classes on the wrong end because, as the devs said, they do not want every dungeon full of arcane-immune elementals. Each one should test groups in a different way, so every class gets its moment to shine somewhere. They also admitted it can be frustrating when it is your class that is struggling, but that friction is simply part of what makes the dungeons feel like real places.
Raids are a separate story, though. The team said it is not ready to talk about how immunities will work in raid encounters yet.
You Can Test It Right Now
If you have beta access, City of Dalaran is open for testing as of the October 8 build, and the beta can be played until October 21. Tuning is still moving from week to week, so treat everything here as subject to change before WoW Forever launches on November 4!
If you have a Mage on the beta, this is a good week to bring it in and see for yourself. Just do not expect to solve every dungeon with one school of magic...
Want to hear the devs explain it themselves? The Dalaran and immunity part starts around 37:00 in the episode below.