In absolute fairness to those who've responded, Tapper's opening post was so extremely brief it didn't really explain her situation at all. However, it never fails to bemuse me how the anti-stepmother brigade immediately leap on what is, after all, a very general remark without stopping to consider for a second that someone who's posted such a short and to the point comment on the stepparenting board almost certainly did so with a significant back story.
IIRC, Tapper has described what sounds like an intolerable position in previous posts, where her DH isn't "putting his children first" in the way most of us would think of but allowing them to behave with complete disregard and a lack of respect towards his wife, i.e. the other adult in the home. Any time she objects she's verbally attacked and again, without searching for her posts, it struck me (if she's the same poster) that she's been relegated to some sort of household appliance there only to service the "needs" (wants) of the rest of them .... what she thinks, how she actually feels .... that's all now irrelevant.
As others have said, and as ever, this is yet another DH problem - although I do think, regardless of the sorry circumstances that have brought these kids into the OP's home full time, that at their respective ages these kids are old enough to show some basic manners. They too are also responsible for trying to ensure that everyone can live together - it's not as simple as letting them have their own way - and that being the only way the OP's DH accepts.
I agree counselling may be useful as a last ditch attempt to sort this out. I appreciate the DH is probably acutely aware that there is now literally nowhere else for his kids to go and of course he'll be concerned about what they've been through - but to my mind, that makes it even more imperative that he works at thrashing out a way of living which accommodates everyone and is also best for everyone (allowing your teen to laze about perpetually will do him no good at all ...). And therefore, I don't understand why he's been so quick to dismiss his wife's feelings - the kids matter, but so does she, and he is the link between her and them. It seems as if he's concentrating all his efforts on making them feel "good" but leaving his wife to sink or swim - with an attitude of, in effect, if you don't like it you can get out. Where is he working with her over this ?? It must be hugely horribly hurtful and in her position, I'd be bewildered at his approach.
So yes, by all means try counselling if only to convince yourself that at least you've done all you can to try and sort this situation out. But no-one would blame you if you decided to cut your losses and get out either. Although it's a hard thing - and this is something counselling might also help with - you may have to face up to the fact that the man you thought you knew wasn't really him if that makes sense ? Sometimes, it takes a crisis for people to show their true colours.