Jody - my son was in therapy from age 6 to 18 (though those last few years were iffy at best, LOL). It was always 1:1, thank you and his therapist. We were never there for the sessions. We would touch base with- the therapist before thank you went in, just to update on what was going on, but that was it.
Did it work? Not immediately. I think mainly he just learned to talk the talk and for us the short-term effect was that he was able to manipulate people (professionals) ever better. I asked the same question you're asking now - is it worth it? What I finally decided, with the input from the good folks on this board, was that at the very least, thank you was getting exposure to tools he might be able to use someday, if he ever decided to get invested in his life and well-being.
We participated in "family" therapy only when absolutely necessary. We had to when he was in RTCs, and of course during his hospitalizations. After one particularly nasty session with- the whole family when he was 13, I stopped letting the sibs participate. They didn't need to be subjected to even more of his emotional abuse. But I even cut off family therapy with- just him, husband, and me when he hit age 16 or so. My take on family therapy is that unless you have a *really* good therapist who will cut the difficult child off fast, the sessions turn into parent bashing, endless regurgitation of how *we* messed up our kid, how *we* are to blame for all the behaviors, how *we* are the only responsible and accountable people in the room. I got really sick and tired of hearing that if I did X, Y, and Z, all would be rosy in gfgland. Bologna. And thank you got really *really* good at coming up with- X, Y, and Z, and then coming up with- excuses when I did X, Y, and Z, and he *still* was violent and out of control - it was my fault, of course.
I think therapy did do him some good. He's a bit more aware of his moods and triggers and behaviors than the average young adult, and he knows what he should be doing to take care of himself. Doesn't do it, of course, but... that's not to say that someday he won't get tired of living the way he is living now and might actually start doing what he knows he needs to do.
So, I guess my answer is that 1:1 therapy, where the focus is strictly on the child, might possibly be worth it in the long run. I don't think it hurts. Family therapy, at least in my experience, was a waste of time and if I had to do it again, I'd just say "no, thank you".