I kind of want to say, gear and builds go hand in hand... But if you want to change your build to go with the gear you have, swap out Energy Armor or Magic Weapon (whichever gives you the smallest paper DPS boost) for a more passive source of Arcane Damage. Something like Arcane Hydra's (for damage) or Black Hole (for CC). That should give you some extra procs off Tal Rasha's. And maybe replace Unwavering Will with Dominance or Audacity (If you're standing still while using Archon... you're doing something wrong ;-)
I'd say stick to one damage type. Or, if you really want to mix damage types, use the Elemental Exposure passive. High DPS isn't the only thing to look for in a weapon. Try to get some elemental damage or a build/game changing skill boost (I like GoO for survival). Also, as you're using RoRG, craft a couple of pieces of Aughild's, I'd say sholders and bracers* (I think Aughild's bracers exist, not 100% sure though).
As far as your build goes, the triple buff single spell build may give nice paper DPS and high numbers, but using spells like Meteor or Hydra with a main spender like Arcane Orb will give you better actual DPS.