Offizieller Kommentar
The short answer is no, but the longer answer is yes (with an asterisk).
If you're willing to deal with some compromises and mess around with the configuration, it can work... it's just not pretty. In my testing I've found it's possible to create an aggregate device (Mac) to connect the DJM-250MK2 and a DDJ-RB and it working, but you'd need to do some modifications to things like the MIDI mapping as the DJM then thinks it can control the mixer when it shouldn't...
If you're on a PC, I wouldn't recommend it at all.