For Archon Shards I use
Tauforged Yellow for Cast Speed
Yellow for Cast Speed
Two Green for Increasing Corrosion Stacks
Tauforged Red for Duration

I won't lie and say you're going to fullstrip much with this set-up, but the Archon mods have incredible synergy with Prismatic Gem, allowing you to kill even Lv 205 Exo Gockstads comfortably with a few casts of Fractured Blast while Prismatic Gem is active, while refilling your energy at a tremendous pace, meaning the negative efficiency isn't a problem.