In my opinion, Thunderstorm should be rather changed like this (
http://elementscommunity.org/forum/index.php/topic,23667.msg323344#msg323344).
The reasoning for the 2
cost is the following (compared with similar mass-CC cards):
3
Pandemonium - Deals random damage to both sides on the field, but the damage is most often than not is more severe (average 3,2 I believe).
7
Rain of Fire - 3 damage to enemy creatures. Expensive, but Fire has easy quanta generation and many other cheap ways to deal with the weakened survivors.
2
Thunderstorm - Deals 1 damage to enemy creatures.
Though Desiccation costs and deals the same amount of damage as Thunderstorm, it also wounds creatures on your side. And while it can still serve as a mass CC unupped, it's better off as a quanta boost around mid game, I believe.
The main problem with Thunderstorm that it needs dedicated (counter?) deckbuilding to find its use, but besides that, it's just weak in every way.. XYTWO's idea would be an awesome remedy for that, but that's for another thread.