Overload. Your aether res is low so here’s the first reason. Secondly, AAR builds have a lot of crit dmg so investing in oa gives great returns in dps.
Nullification is always nice to have. You can remove damage absorption buffs from some enemies like Valaxteria or the Councilmen or cleanse yourself from Anasteria debuff. For a long time top builders used to invest in it till 10/10 even.
There were a few points wasted by going over the cap like Mirror, Mental Alacrity, etc.
Fabric of Reality was just nerfed along with the AAR conduit so I’m not sure if going over the cap is still viable.
What I didn’t do, though, is take Devastation which synergizes very well with Aeon and Violent Decay belt.
For devotions take a look at my AARMAGEDDON build or RomanN1’s build (currently the best guy for AAR results) or this build: [Caster] [1.1.4.0] AAR Spellbinder Neon Light Celestial God Slayer (g4) (c+) (sr+) (vid)