I see. Thanks this is really helpful. I guess now my question is the difference in these two options isn't concrete because you may need to wait a few seconds for a tick after the transpose - wouldn't it be helpful to get used to casting T1 for long-living mobs in order to proc more thunderclouds?
EDIT: nvm I see you've accounted for the transpose wait time (3s in your calculations).
EDIT2: Since I have your helpful attention, here's another question: how many mobs would it take for 1 thundercloud proc on a non-DoT'd mob to be more potency than a Fire II? Or vice versa if a thundercloud proc is more potency by default
