IMO the best arcane build is centered around the Prophet of Wrath legendary enchant. You can focus on either magic school (Holy/Arcane) as the divine damage will scale with your highest of either spell school, Since you mentioned wanting Arcane I weighted the talent and RE choices for that.
The talents depend on if you're playing Area 52 or Thrall. Here is an example build:
https://ascension.gg/v2/builder/thrall/overview/99fcafd2-0d16-4c9b-a756-b4270f2198d2
Mystic Enchants:
Legendary - Prophet of Wrath
Epic - Harnessed Energy (Allows you to open with a single Arcane Blast, only refreshing to maintain the Stacks)
Epic - Power Overwhelming/Glyph of Arcane Missiles (I haven't tried Glyph of Arcane Missiles, but theoretically it might be better if your fights aren't lasting long enough to use two or more Arcane Powers.
Epic - Swift Justice/Holy Magics/Prepared Ritual (Swift Justice is incredible, but you can drop it if you really want.)
Rare - Arcane Empowerment x3 (6% bonus damage...yes please)
Rare - Missile Barrage x3 (Arcane Missiles is what allows you to maintain DI uptime. This is mandatory.)
Rare - Hasty Divine Illumination (x3 or until you can keep this buff up 100% of the time.)
Rare - Celestial Focus (Haste is very important to this build. This makes up for dropping one point in the Alacrity Talent.)
Rare - Raw Light x3 (If you're hit capped and don't need Hasty Divine Illumination to reliably keep DI active.)
Rare - Precision (Prioritize this over Raw Light if you're not hit capped.)
Rare - Balance of Power (Prioritize this over Raw Light if you're not hit capped.)
A few additional notes:
There is an argument to be made for Clearcasting + Arcane Potency as talent choices in this build.
I made an assumption that you have another source of applying a movement/attack speed slow to your target. If not, you'll need to pickup Slow and the Unfurling Time RE.