As with PhD's, you have to want the DMin for its own sake rather than a stepping stone to something else. Most people will not be teaching afterward with either, though it can develop someone's skills usefully. Probably the majority of PT faculty at Reformed seminaries have DMin's. alongside pastoral experience. Counseling is less likely to have a DMin, though not impossible, especially in less integrationist schools.
In terms of the marketplace, there will be ever growing opportunities for adjuncting and serving online programs in the years ahead, as a side interest, not as a career. There will be steadily diminishing opportunities to teach full time in seminaries and Christian Colleges, whatever your qualifications.
It's also fair to say that not all DMin's are equal. I've read theses that would have sailed through a PhD program and others that weren't worth the paper they were written on. If you want to teach, you should aim to be closer to the former than the latter.