I really am curious where the idea of Thunder II cast + Thunder III for procs came from. Do people have data on this? The tool-tip explicitly states if you use Thunder II for the dot, your thundercloud procs will have a 295 potency no matter what rank thunder spell you use to trigger it. Whereas using Thunder III gives a 345 potency thundercloud proc, again no matter what rank use you to trigger it.

So if you cast thunder II and a thundercloud procs, you can hit Thunder I, II or III and they will all do the same damage. There's no "bonus". Is using Thunder III for procs, putting up Thunder III's dot(instead of re-applying Thunder II's) and then that turns all future Thundercloud procs into the 345 potency instead of 295, until you hard cast thunder II again?

I'm not seeing the benefit of losing 50 potency per cloud proc for .5 seconds of cast time(outside situations with tons of movement).