I had asked this previously, but I guess since they both do the same thing and work with WIM files, there wasn't much impetus for LD to make a change.
I read somewhere that MS would be expanding the capabilities for DISM and if they do, it would be nice to have those natively in provisioning. Doesn't seem like this would be a heavy lift for LD since they already use DISM in WinPE for HII driver injection.
Maybe we'll be able to find something out about this at Interchange.
Obviously it works fine using ImageX, but I have to admit my initial reaction when first seeing this was I wondered if there are differences in the .wim file format between ImageX and DISM. I don't honestly know and suspect probably not, but that voice in the back of my head wants to know if down the road there might be some difference. We were using LANDesk v9.6 and just now implementing 2016 and I guess I kind of figured it's been multiple years since ImageX was deprecated by Microsoft and just assumed DISM would be used in this newer version of LANDesk. Like I said, not a concern at this point, but it was kind of an obvious question in my mind to ask.
LANDesk's ImageW works great, but so does ImageX. We are currently using ImageX with our Win10 1607 and 8.1 images just fine. We are only using ImageX because we just started doing BitLocker pre-encryption of used space so save time on the provisioning process. The only other advantage to using ImageX / Wim's is the offline servicing you can do, but I found that a lot of Microsoft's newer roll-up patches do not allow installation via DISM / offline servicing. If you are not going to do the pre-encryption or offline servicing, I'd stick with ImageW because the actual imaging process is a bit faster with it and it is less complicated. I don't have an answer to your question, but hopefully my reasons for one vs the other will help you out.
That's another change expected in the next dot release, as I understand it, later this year. It doesn't affect functionality, so it's not a priority change. I think it may open the door for some other enhancements once they do it though, so here's hoping for that...