
Water Magic: 12+2
Energy Storage: 9+1
Fire Magic: 9+1
The major combo here is Mirror of Ice (66 dmg + 6sec 66% slowed snare) + Elemental Flame (+56 burning dmg while acting as a cover enchantment for Water Attunement). Mirror of Ice is a dual cast, nearby range aoe hex. What happens is the ele hero in the back dual casts the hex 'on me' the front liner, so the resulting aoe is massive because it hexes enemies in nearby range for both allies.
Ice Spikes and Rust (which are adjacent sized aoe dmg hexes) also spread aoe burning and ensures Mirror of Ice's recharge is halved to 7.5secs.
The last 3 slots are optional but I put GoLE, Glowing Ice to stupid-proof any hero e-manage problems, and Blurred Vision as an alternative to Aegis.
I looked into Shatterstone but the 3 second delay, reduced dmg due to armor, and smaller aoe results in less DPS.
Anyway, if you want raw damage from an ele just run GoE+Lightning Hammer+Orb+Chain, but this specific build synergized well with my Derv due to the massive spammable snare.