The only way I've found it viable to use is like this (my main is a 70 lock):

Make sure you're using an adon that allows you to see pet's cast bar.
Make a focus macro that casts (and recasts) seduce on the focus target so you don't need to switch targets later.

Now, to avoid the succy being 1shotted, and then the mob moving onto the healer after it's dead, have a macro that does the following: Attacks the /focus mob with searing pain, and tells seduce to cast, so that the mob gets smacked with a very high aggro spell and then seduced. You might need 2 macros for it anyway tbh, to make sure SP lands b4 seduce. If you'r not multi-boxing this is less of an issue

Now you watch the pet cast bars, the second they stop casting (it's a channeled spell) it means seduce broke or finished. Recast the seduce macro, at worst the warlock gets smacked once before it's re-seduced (make sure you don't try and searing pain again though, it'll get interupted and land late)

It's still not greatly relliable, but at least like this it's workable