Two very good Me/E builds for cantha:
Wards/Interrupter - Everyone loves wards, even nubs, and for once they're actually right. Dump 12 into earth, bring WaM, WaE (tyrian only, so you need to port to sergio in LA to get it, but its worth it, especially against those insane ele and rit bosses), Armor of Earth, glyph of lesser energy, and some domination interrupts like complicate and the power spike (? not sure of name). Arcane larceny and diversion are fun too. You're useful and you have obvious benefits to the party (for the blind wamos). Later on you can bring ward of stability or switch to water and use Ward against harm (which kicks ASS vs all ele bosses and especially argo and his ilk).
Earth disruptor - basically a damage build for those who don't like to sit on the sidelines and protect/defend. Unsteady ground does in fact kick ass. Skills (used in this order): Auspicious incantation, arcane echo, unsteady ground, glyph of lesser energy, dragon stomp, unsteady ground. If you're packing ele offhands and wand, you ahve a good chance taht you can recast both unsteady grounds again, making for a VERY nice stream of knockdowns. Dragon stomp also has a short recast, though exhaustion is a pain. Maybe pack a quick kd like tenai's wind, though this would force you to enter melee range.
Alternate build - using tenai's wind, aftershock, crystal wave, and shockwave. You can dish out MASSIVE damage, though your energy will plummet. Make sure you have earth attunement. Echoing shockwave or ashock and using tenais wind + whirlwind can multiply your dmg output, but put your energy out of commission sooner.
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But the real winner is someone with low lag who can interrupt constantly... I lose to that alot, and I lag more so I can't stop stuff sometimes 
).