I did a small test on a sorc, and I think the same applies in that case.
- Cast velocious curse on a target, get a certain amount of damage (let's say 1000 to make it simple)
- Cast entropy to get the damage buff, then cast velocious curse, the curse hits for increased damage (let's say 1200)
- This time, cast velocious curse, and then entropy: the curse hits for 1200, even tho it was cast before you get extra spell power.
This leads me to think that Magic detonation / healing ward will benefit from increased spell power / healing.
This might be different for bats, and prefer to remain silent on this until someone can confirm whether it's the same mechanic.