Currently Ele Shaman is the ONLY class that 2p set bonus and 4p set bonus provide 0% damage increase, if you can find another class or even tank, name it.
Due to Lava Burst 2 sec cast time scale issue , it does less average dps comparing with LB in naxx with wb so 4 set is useless. every lava burst cast will lower the dps. So this bonus is either 0% or minus percent to elemental shaman damage.
Without Lava Burst, Flame Shock is useless too. It does almost same damage per second comparing with lighting bolt, however lightning bolt can trigger rolling thunder as “extra damage” so use flame shock will only lower the overall damage.
(2) Set : [Increases periodic damage done by your Flame Shock ability by 20%.]
(4) Set : [Reduces the cooldown on your Lava Burst ability by 2 sec.]
Suggestion:
(4) Set : [Reduces the cooldown on your Lava Burst ability by 2 sec, refreshing the current flame shock on your target and instantly deals 50% of the damage done by your flameshock.]