Okay after playing & leveling up a Mag/Stam/Sup Arcanist I've decided that I'm going to put my feedback on them! (I don't play Tank classes because I'm a beta so it wont be included)
I'll start off talking about Stamina Arcanist. There are a few things that make this choice busted but I'll go ahead & name the main thing. Cephaliarch's Flail (Abyssal Impact Morph).
This skill is so over-tuned that your great grandma could play the game. For those who don't know what this skill does it does the following...high damage, low stamina cost, heals (you don't even need to hit anything), immobilizes, generates crux, increases your damage by 5% & it's an execute at 50% hp & lets not forget it also has a cast time of .3 seconds & is aoe making it even more op with the deadly set. If you pair this skill with Spiteward of the Lucid Mind (Runespite Ward Morph) you legit becoming unkillable. Infinite healing & shielding at this point. Who needs mechanics when you can just ignore them with the absurd sustain that Stamina Arcanist has. When playing this I legit never dodge mechanics & I stand in the fire. - Easy balance fix remove the heal and lower the execute threshold to 25%
Alright here we go! Magicka Arcanist. Overall it has solid damage and the sustain is okay, (no where near Stamina Arcanist though).
So your main way to generate Crux as a Magicka Arcanist is Runeblades, after that you have 2 ways to dump your crux essentially. You could use your fatecarver for damage or use Runespite Ward for some health/shielding. Technically you could use Tentacular Dread (Abyssal Impact Morph) for 60% more damage on the skill but remember that's really all you get other than the immobilization. No health back, no execute. I guess you could use the stamina morph but rip your stamina sustain. Magicka Arcanist is in a fairly balanced spot with all things considered. Even though Stam is way better that is just Stam being overtuned.
Finally lets talk about support Arcanist! Both low level & high level content has been a breeze with this. I'm a healer main in almost every game I play assuming supports like bards aren't an option. You can play healer not only as a magicka user but even a stamina user with this class. Personally I opted in to a medium armor resto staff stamina healer with like 5.3k stam regen.
Being a magicka healer brings in raw healing as stamina is more of a buffer/shielder I've noticed. It does pain me to say this but I do feel like the shields that Arcanist brings to the table do need a tad bit toning down. Chakram Shields (both morphs) You are able to ignore a lot of boss mechanics since you can keep a 13k+ shield on everyone that also heals if you choose that morph. - Give shielding a diminishing return & that should balance things out.
Here are some honorable mentions of busted skill that do need to be balanced in certain areas of the game.
Gibbering Shield & Moprhs - This extremely busted in PVP it essentially makes anyone unkillable for 10 seconds. Shielding needs a nerf in PVP. Pretty much the same thing in low level PVE but it's actually not op in end game PVE since things hit like trucks anyways.
The Tide King's Gaze - This is also pretty over-tuned in PVP making the other morph 100% useless.
Runespite Ward - Shield is way to strong in PVP & it also heals.