DoTs, Blades, and Traps question

So from my understanding Blades apply to the initial hit and the damage over time on other turns.

Traps and feint only apply to the initial hit?

So if this is true (someone please clarify if any of this is even true or not) then feint, which is a good spell I know, is not good for damage overtime. So is it worth to even train it for fire student. Like I guess it’s still god for meteor or phoenix right?

Sorry. I know I’ve posted a decent amount askin things.