Apparently, it is not, as the balance has not yet been achieved.Our spec has already been redesigned three times this expansion (originally, quickening redesign, quickening removal). Isn't that enough for one expansion?
The changes they made were rather drastic if you think about it. The quickening made us change play-style and stats completely several times. Don't get me wrong, the original Quickening was just a stupid way of pressing NT until you get AM proc, I can hardly imagine more boring way of playing wow except pet battle championship.
Nevertheless, it was a huge change and because of that, we are (in a way) where other classes were in the beginning of Legion - in their first/second "live" version, yet to be polished.
My personal experience (been arcane ONLY since this expansion launched) can only confirm that. Diversity of talents in raids is about zero, stats are still out of place as they are directly implied by your current legendaries. Raid mechanics are extremely punishing for us, we lose vast majority of damage output if we are forced to move excessively.
I am, for instance, fine not being able to do solid cleave dmg. That comes with class identity, you cannot ask to be a jack of all trades (well, talents should address that; and in a manner they do, but you lose too much single target dmg then).
But I would welcome a bit of diversity in playstyle (just making Temporal Flux a comparable option would achieve that).
Also a steady dps output, based on your skill rather than RNG, would be very welcome. RNG here being how many AM procs you get plus how many mechanics you suffer from - you can cast AM while moving so that provides DPS while moving.
Every week in NH I can see this; I dare say I am pretty capable player as Arcane, not exactly mythic raider as I don't wish to commit so much time to it, but otherwise I did all the other challenging parts of the game so far (Curve, Kestone master long before it was cool, artifact look,...). And I am usually amongst top DPS but I can see how strongly that waivers with the raid mechanics I have to deal with and how certain classes stay unaffected by them (losing only small portion of dps). That's the thing to tackle if you ask me and arcane explosion is not a way to go (oh, hello there Time and Space).