On the test server, I managed to get a raid of stormstrike shamans and a Power Infusion specced priest to get the highest crit possible in world of warcraft with my chain lightning. The target was a level 60 warrior sitting in zerker stance. In this video, I have a lot of +DMG gear and a lot of buffs.
This video features 2 MASSIVE CL crits. ~25K'ish
My suggestion to blizzard:
Change stormstrike so it doesnt stack many times. But instead, give stormstrike an unlimited amount of charges (make it a real debuff) for its whole duration. Then, it would be like a shadowpriest shadow vulnerability.