I didn't use them, but I don't think that they are bad per se.
They just weren't that good to use for my play style.
Especially, since by the time I got them I already had characters that overshadowed them in everyway.

I probably would have used them though, had I had a few more places in battle.
Since, I don't see an option that appeals to me I'm just going to vote that they are useful, I guess.