I'm actually a lower ilvl than you but my DPS is sitting around 348. The number one reason for this I'm sure is that I don't save my procs. When it procs, I fire. There's really no reason for you to save them. I can see saving your thundercloud proc for just a few seconds to squeeze out a little more damage with the first thunder you casted but I wouldn't wait so long as to lose the proc. Also, the sooner you use it, the sooner your chance of having another one to use will arrive. Whoever is telling you to save the procs must be a horrible BLM. Saving your procs is never better than shooting them off.