Solo tricap build with some insane damage output. Your buff duration is around 70 sec so you should be able to kill the entire eidolon within that time frame with both your [Shock Trooper] buff and can stack up to 6 shields in plus electrify them with his passive to hit the one mil damage numbers on the eidolon depending your sniper and build.
For the reason i use arcane nullifier is since I'm using madurai as the focus tree for the damage buffs and void strike. I just go into void mode once a joint has broken.
For the other arcane you can go either [Rage] or avenger both are nice for damage but in different ways. I'd use [Rage] if your using the [Lanka] or [Vectis] since you're more likely going to do more damage with the [Rage] buff then you are with the higher tier crit hit.