Going to add some more thoughts here on Arcane (and mage in general a bit) at a more mechanical level.
Mage pays a price for movement.
I’m OK with that, generally, as it makes sense. However, IMO the price is too high and the 8.x shimmer shows it. One thing I’ve kept in mind over many years of game design is that if you have a spell, power, or ability that is a must have for pretty much everyone - you have something broken. Either the capability is broken or something in the class/base is broken.
In this case, it isn’t that shimmer was broken but that the core class mechanics are. We all take shimmer because we basically have to. Why do we have to? Because the encounters force us to. Every few GCDs you have to move because Blizzard loves to “put stuff on the ground to kill you” (you can see this even in Starcraft 2 and Diablo 3) as their means of making encounters “more difficult”. This automatically, and unavoidably, adds a tremendous cost to any class that takes a penalty for movement.
To account for that either you need less forced movement, or the movement penalty needs to be lower. Displacement/Shimmer being mandatory exposed that problem and somewhat accounted for it by reducing the cost of it. But it also exposes the other part of the problem - especially for arcane.
This is where arcane’s additional penalty comes in: the ramp up. Arcane pays a heavy price for its DPS in the sheer number of non-damage (or low-damage) GCDs needed to get into stride. On its own that may be a reasonable price to pay. However, what we have is a combination of the two and this gets to be too high as a result.
With arcane you have to spend several GCDs to get to do decent to good damage. Now add into that the need to move every 2-3 or so and you can see the penalties stack up. For a mage, especially an Arcane one, movement is functionally a longer GCD; the longer you need to move, the longer that GCD is.
This needs to be taken into account to make Arcane a better, as in more fun but still effective, class. Consider what we can do while moving: Arcane Barrage and maybe a supernova. The former means going back through the build up - thus paying the GCD price again, and the latter is on a longer CD and has little damage/effect. So neither of these are a reasonable expectation - especially the former.
This is where the encounter people and the class people need to coordinate better. If I have to move every few seconds because fire bad, and I have to spend longer than that building up, and I lose significant DPS while moving, I’m not having a good time. It is like RNG on top of RNG on top of RNG - moderation is needed. Especially when encounters have “move around for many GCDs” baked into them.
If we stick to the Arcane being a form of chronomancy, it would make sense that some of Arcane’s features involve getting around that using some form of temporal interaction. Shimmer taking blink off of the GCD and usable while casting demonstrates this problem and why we needed it and have such a problem with it going away it “solved” (to some extent) that confluence of problems.
Now the good thing about Arcane Blast is that the buildup isn’t per-target but on the caster. This is especially good for trash/solo adventures. The bad thing is that it takes 3-4 casts to really kick in and that you have to stand still to cast it. I’m pretty much OK with that, really. I have no problem with the increase in mana cost either. In fact, this may be why I love having mana gem back. Using a mana gem is something I can do while moving. It doesn’t do damage but delays needing to use Evocation which lets me DPS more.
Arcane Missiles, however, is a bit of an issue. I think a good change to it would be to leave it channeled, but not have movement break it. You have to stand still to start the missiles, but having to move wouldn’t cut it short. If we didn’t have to move so much then perhaps that wouldn’t be so bad.
Now for blink. First lets acknowledge that blink is basically broken. We’ve all had it happen: blink to get away and find you “blinked forward” approximately one step. WoW isn’t the only place Blizz has this problem (exactly the same one in D3), but it is a problem. Two charges on blink felt to me like “yeah we know it doesn’t work a lot of the time so lets give you another chance for it to fail to account for it”.
So how can we make that better - short of fixing the base problem there? Check distance blinked and refund the charge/reset cooldown if you blink less than X distance. With that we can then let blink be what it should be - making movement less crippling for arcane mages. Make it being off GCD core. not necessarily at low levels perhaps - maybe one of the “level rewards” is a passive in the arcane leveling progression along the lines of “Blink becomes Spatio-Temporal Warp, removing it from the GCD and doesn’t interrupt casting”. The sample name here applies a time based theme for flavor.
While that doesn’t address prep-time, it can help significantly with the GCD+Move penalty stack. A “more intelligent” Mirror Image version like I mentioned in my previous response could soften the movement penalty a bit more - you could use it to time some DPS maintenance around move-heavy phases and/or use them at will if you know you don’t need to.
On that note, here is an idea I just had for “Temporal Clones”: A talent line for arcanes that lets you select the spec for them. More of an alternate timeline idea where you pull in “clones” that specced into Frost or Fire to give you some added functionality, such as Frost clones throwing frostbolt for 1-2 targets and blizzard if >2. That could temporarily (eheh) give some AoE capability to arcane. Selecting an alternate arcane timeline for arcane would require a bit of thought.
Hmm, perhaps your arcane alternates’ Arcane Blast count as being cast by you in terms of ramping up. For example during movement you might throw the barrage, dropping your blast stack and pop clones which then cast blast giving you three stacks back. That might be interesting.
Anyway, this post is plenty long already and my stomach is demanding some breakfast, so I’ll close it here and think some more on that last bit while making and eating breakfast.