Could it be the skill itself? I am just thinking outloud but is it possible flame crits less than say lightning?
I don't think so. On mobs, my instances crit as often as Flame.
Tried Crit Pot yesterday, at 76% crit. First 2 bosses I was able to crit around 30%, which is a bit more than what I usually crit for. But third boss, only critted around 15% or so, and 4th critted 40%, about 5-10% less than what I usually crit on that boss.
So, looks like back to Arcane pot for me. Also tried matk food, and didn't see much difference in crits between 140k ish matk using Mdam and 175k ish matk using matk food. Although I seem to hit for the same damage on both, so I guess I'll use matk incase Ziav is right