Yesterday me and Lizandra discussed the Thunderstorm rotation a little, came to the conclusion that it's best to have your grounding totems included in the rotation of TS.
For those who are new to this or not aware.. what I do is that I have 4 separate buttons, each with the same but rotated spells around the shammies:

Button 1: TS, Grounding Totem, Fire Nova Totem, Grounding Totem
Button 2: Grounding Totem, TS, Grounding Totem, Fire Nova Totem
etc, or something similar optimized for your needs

Should preferrably be used in succession B1-B4 to maximize effect.
On a side note, the reason I don't use cast sequence is that they are unreliable in PVP with all the CC and silence going around - they get way out of synch. Using these buttons in pvp I spam them as needed until the TS goes off.

This rotation has improved my pvp performance immensely in BGs. Knockback + aoe stun + spell defense in one single button press - it's simply an awesome tool to survive the onslaught of many enemies.. The thing to look out for is to not waste TS on nova stunned targets.
I used to have Frost shock and no groundings in the rotation, but the frost was sort of counter-productive, because meelee that was TS:ed and frosted sometimes didn't get back fast enough to get stunned by the Nova.


Edit: Note that "TS" in this rotation is a macro with pvp trinket + TS which makes it more useful under pressure where you are often stunned or polymorphed or whatever.