To give an example - this is what you will be looking for in PvP:

* Elemental Mastery
* Flame Shock (high chance to crit)
-> Elemental Oath
-> Clearcasting
-> 10% increased dmg from spells (sick!)

* Lava Burst crits for 9-11k.. I assume.. pretty ridiculous dmg if you manage to land it.
* Chain Lightning with high crit chance if you still have EM active.
* Earth Shock/TS


So, if allowed to cast, a 4x shaman team will probably be looking at landing 50-70k burst damage on a regular basis. Not so bad after all.