To start off, I understand that everyone has been begging for a new class for years. As a business decision, its a great one. It will bring in a lot of money, which is how ZOS seems to gauge their actions by. Given the current balance issues in both PvE and PvP, or really, lack thereof, I believe a new class will only make it worse. Warden and Necro both did when they came out. The current system of nerfing classes and buffing 1 or 2 classes up too much isn't healthy for the game.
Granted, when Arcanist comes out I'm sure it will be buffed to immense proportions, like every other gear or mythic as a selling point for a new expansion.
So why Arcanist? Bard was a frontrunner on what I had seen people asking for, and it would have been a good return to Skyrim. Heck, we could have brought in bard as part of Western Skyrim with a better Bard's College questline. Although given that Necro had come out the year before, I didn't expect a new class the very next year.
The thing I have noticed however, is that every single race in this game has had an expansion tooled around them except Bosmer and Redguard, though some races prominently feature in more than 1 chapter. It would still be possible to do, even though most of their land is already base game. I had hoped for at least a Wood Elf Warden companion, but for some reason its an Argonian. At least the new class is a Redguard companion.
But if you want to play the new class early, head to FF14. Since Zos is so bent on copying a class from a more successful game. Granted, Arcanist on FF14 is a lot of fun, at level 30 it splits into Summoner (Mag dps) and Scholar (shield healer). It's a popular class, I can hardly blame them, and yet our first class in years should be more original, or more specific to Elder Scrolls, rather than a green sorcerer with tentacles. Something different would be nice, and Warden brought that when it was released, it was different from the current classes. Did I mention both classes that stem from Arcanist use a spellbook as a weapon?
Even the "new" Crux system is inspired from FF14. The Aetherflow gauge that Arcanist has in FF14 is fairly similar, still different but works similarly. Certain actions fill the gauge, which then opens up a couple new skills to use. Now, Crux varies by getting 3 stacks which can then be used to buff your current abilities.
I have no doubt that I'll enjoy Arcanist in ESO, I felt the same way about both Warden and Necro when they were coming out. I've enjoyed both classes, but they did do what I feared and make the balance issues worse. As someone who does both PvE and PvP, I have seen the balance issues on both sides. As I said earlier, the current "balance" system does more harm than good. I hope that ZOS looks at this, not as a huge critique but as a plea to balance the classes, to make the game more fun. I sincerely love this game, I started playing on Xbox 9 years ago. 4 years ago, I moved to PC, and had to start completely over. Take good care of your playerbase, and they'll do the same for you.
As a side note, I'll also be happy if Arcanist's portals aren't bugged so people can port into enemy keeps with them. I will be interested to see how the class functions in PvE and PvP.
As far as the endless debates for PvP and PvE, we all play this game. We all love this game. I've seen both sides blame each other for nerfs, and it's really no ones fault. Everyone deserves to have fun on the game, PvP players deserve to have fun in a less broken PvP experience (and bring back the double tel var event, Hakeijo prices are skyhigh with no checks and balances that the event brought for that market). PvE players deserve to have fun in their PvE land.
Sorry for the long post, I tried to explain myself as best I could, and to be as gracious as possible.