Arcane is deceptive on several levels. Arguably the "simplest" mage rotation (and maybe one of the simplest rotations in the game), its few buttons hide a complexity of nuanced play that rewards careful planning and understanding. It used to take an entire addon just to manage an arcane mage's mana bar. This seems like a good sign that there's more going on underneath the hood than you might think.
Arcane has three primary single target spells to use: Arcane Blast, Arcane Missiles, and Arcane Barrage. All of these interact with Arcane Charge (this is the offspring of the old stacks of Arcane Blast's buff). It stacks to a maximum of four and increases damage done by various spells depending on the number of stacks, but it also increases the mana cost of Arcane Blast. Arcane's mastery comes into play here, and is the reason why you can't just cast your spells helter skelter and never consume the charges. If you do this, you'll run OOM and your damage will plummet like a rock dropped from Dalaran.
So the new arcane is a careful balance of generating Arcane Charges and then resetting the charges before they get out of hand. You also have to factor in the usage of Arcane Power and Alter Time, usually accomplished through macros. Oh yes, and don't forget to manage your Rune of Power, dropping it where you might expect to be and refreshing it even if you're standing in one spot.
At this point I hope it's clear that I don't believe arcane's gameplay is simple at all. Or, if it is, there's an elegance to the simplicity. Maybe you can pick up arcane and perform reasonably well while only knowing the basics, but if you take the time to truly understand the interactions between arcane's spells and buffs, playing it to its maximum potential becomes more complicated than you'd think.
This is where the second challenge facing arcane comes into play. Whether or not arcane is simple to play, the public perception is that it's simple. It's hard to quantify the effect this can have on a spec, but it's not an insignificant one. Remember when no one thought that frost mages were "viable" for PvE content? Well, the popular opinion about arcane is that they can't possibly be skilled players because their spec requires no skill.
We know this isn't true, of course, but if your raid group teases you about being a spec or people link images like this one:
It's hard not to take it a little personally. It's a frustrating position to be in to carefully micromanage and line up all of your cooldowns, plan your Rune of Power placement, respond to procs and make judgment calls about when it's best to reset your Arcane Charges - and then have some guy named Lolustink single you out to be mocked in an LFR pug. Maybe it becomes a self-fulfilling prophecy. You know on some level that what you're doing actually takes skill, but even other mages are derisive about your spec. It's possible that some part of you might start thinking, "I'd like to try out fire...Yeah, fire would be nice."
What people think about a spec and what a spec is are of course inextricably entwined. Does arcane have fewer buttons than some specs? Yes, definitely. That's where this thinking comes from. Is the solution to give arcane more buttons? Not necessarily.
Mages already have many cooldowns, buttons and abilities to manage, regardless of spec. We don't know what the future holds for our talents, but for right now every mage has to manage their tier six talent. We all have to know how to leverage Alter Time to our best advantage, and learn when to use Time Warp in a given encounter. We've all got an armor, and a bomb, and a movement ability. We've got plenty of things to push. Preferred specs often come down to taste, when DPS performance isn't a factor. To some people arcane just feels "right." It has a metronomic rhythm that can be almost hypnotic. It doesn't have the explosive elemental power of fire, or the cool deliberation of frost, but arcane is the source of most of the iconic mage spells. Arcane mages are the Time Lords here, but they don't seem to get respect for that.
Finally, and most significantly, the biggest challenge facing arcane right now is restriction of movement, period. The other things - a simple rotation, people thinking arcane isn't any good - both of those things are minor compared to how restrictive movement is as an arcane mage. The trend for ranged casters since Cataclysm has generally been to allow all classes some options for when they have to move and cast. This makes arcane in its current incarnation feel like an anachronism. Most everyone has options for casting and moving, and arcane is more rooted than ever.
Arcane mages must take Rune of Power. Invocation reduces passive mana regeneration by 50%. Incanter's Ward reduces mana regeneration by 65% when it's on cool down. Both of these effects are bad news for arcane due to Mana Adept, compared to Rune of Power's 75% increased mana regeneration without drawbacks - besides having to stand in one place. Because of this reliance on Rune of Power, arcane mages have now become the absolute definition of turret style play.
I know I've complained about Invocation before, but really, using Evocation to refresh a buff is a walk in the park compared to Rune of Power management. Reliance on this talent is problematic for encounters that are movement heavy, and also for raid groups that don't tend to be predictable in their movement. The loss of Scorch, even with the use of Ice Floes, compounds this problem. So you have an already stationary spec, that when forced to move, struggles to fill that movement with spells. You may have noticed that many of the current raid encounters involve quite a bit of moving.
Still, mages are resourceful, and arcane mage DPS statistics are noteworthy. There are mages out there who manage the Rune of Power, make it work with the movement, and are able to obliterate others on the meter. I'm sure they would still welcome a change to Rune of Power because it affects their spec more than any other. What if Rune of Power was a single button cast by dropping it at your feet? That would make it much less obtrusive than it is currently with the targeting reticule, something closer to using Evocate for Invocation.
Of course, I'd prefer if Rune of Power just went away altogether. Untether the arcane mages! Set us free! There's no promise of that happening, though, so in the meantime we're stuck with it. Increasing the effect to 8 yards was nice, but it's only a band-aid. The issue of a simple rotation depends on your perspective, and mages are largely divided on this point. The perception of the spec is pretty clear, but not insurmountable, and the movement/Rune of Power issues are something that could be remedied. Addressing only those would go a long way towards helping arcane mages bend space and time unfettered by having to stand in just one spot.