I think it's a good place to discuss thunder spell,
I honestly don't know how does the thundercloud buff works. so let me mutting and teach myself here:
it has 5% chance it will trigger, but thunder effect will last 12s. But the actually ticks will be 4 times? Anyone counts how much times it will do the -hp ticks?

Thunder: initial 30 pot, 40 pot x 4 for DoT expect to trigger thundercloud buff is once every 5 thunders
Thunder2: initial 50 pot, 40 pot x 5 for DoT expect to trigger thundercloud buff is once every 4 thunder2
Thunder3: initial 60 pot, 40 pot x 6 for DoT expect to trigger thundercloud buff is once every 3.33 thunders

at thundercloud buff
thunder will cause 190 potency
thunder2 will cause 240 potency
thunder3 will cause 300 potency
with no cast time and no mp cost...

/muttering off...