Here is feedback about Arcane Sunfury.
Spec is decent and Arcane Soul window feels powerful, but its flow and aesthetic are worse than Fire Sunfury - Spellfire Spheres generate much slower, Glorious Incandescence Meteorites are very delayed and can easily miss (since they appear only when Arcane Orb hits the target and even then have a delay) and you mainly feel like a semi-Fire Mage with aesthetics for both spheres and procs. There could be additional improvements for this spec’s Arcane version to address that and make its flow more smooth.
Spellfire Spheres - like suggested in Fire Sunfury feedback post, please hasten their generation out of combat, for example to every 30 seconds without Rondurmancy and every 20 seconds with. This will allow to align them with Arcane Surge’s CD much better, as delaying its usage till they are stacked to full can be quite bad. Also please consider Arcane Sunfury’s spheres more purple to match Arcane’s spec fantasy, since current look is still more fitting for Fire.
Mana Addiction - for some reason it provides 0.5% Haste per stack just like for Fire, even though tooltip states 3% per stack. Hopefully it is a bug / oversight and will be addressed. If it is not - Mana Addiction still should provide bigger value for Arcane than for Fire since consuming Clearcasting occurs much less frequently than consuming Hot Streak.
Arcane Phoenix - Arcane version could both use a bit of recolor (more dark purple instead of orange) and have a bigger variety of Arcane spells (maybe with some Fire spells replaced with Arcane analogues) to match spec identity, since it still primarily uses Fire spells.
Burden of Power - kinda undertuned for Fire and even more undertuned for Arcane. Assuming you play Nether Precision rotation, you would buff every 7th Arcane Blast by 15% (2.15% average increase) or every 7th Arcane Barrage by 30% (4.3% average increase). That is quite low for a hero talent and could be boosted.
Merely a Setback - same feedback as for Fire Sunfury - please buff it and make it a choice node with other defensive option, since both Avoidance and Leech with limited uptime are not always needed or useful.
Lessons in Debilitation vs Gravity Lapse - same feedback as for Fire Sunfury - please revert Gravity Lapse back to stun and if needed reduce targets number and / or increase cooldown to compensate. It feels bad as a root, is inferior to Ice Nova and Mages simply don’t need even more roots. Seeing Mountain Thanes getting an AoE stun (that does not replace anything) and Hunters getting AoE stun for Intimidate (without even any drawbacks), but having Mage’s AoE stun replaced by another root is very disheartening.
Glorious Incandescence - effect is decent and powerful, but should trigger immediately on Arcane Orb hit without current delay, as because of it enemies can simply run out of area before Meteorites fall.
Savor the Moment vs Sunfury Execution - both options can be competitive, but track performance of Sunfury Execution. Savor the Moment has synergy with Memory of Al’Ar while Sunfury Execution does not, so latter might underperform in the end and could need boost for competitiveness.
Codex of the Sunstriders - same feedback as for Fire Sunfury - can be beneficial to opt out of entirely, so consider buffing Phoenix’s exceptional spells (including Arcane versions if they were added) and making Spellfire Sphere damage bonus persist for several seconds after being consumed to provide less personal damage loss during your major DPS cooldown.
Rondurmancy vs Ignite the Future - same feedback as Fire Sunfury - consider making Rondurmancy hasten both out of combat and in-combat Spellfire Spheres generation (for example via also reducing period out of combat and number of Clearcasting stacks consumed required in combat) to make it more competitive and more likely to stack to full before pull or while Arcane Surge is on cooldown.
Memory of Al’Ar - good effect, but Arcane Soul currently has no UI indication outside of your character becoming purple. Many people play with extremely zoomed out camera and might not notice it much, especially with all the possible events and swirlies around. As such, please consider adding it a UI indication similar to Hyperthermia (large purple arcs to the left / right of Clearcasting UI arcs around your character).