What I like to do is:
-If there are 1-3 enemies along with Dreamrunner, I use Aquila's LT+B attack on the other enemies and focus on dodging and hitting Dreamrunner.
-If there are 4+ enemies along with Dreamrunner, I use DT and quickly target Dreamrunner
-If there are 2 Dreamrunners, or maybe even more, quickly use DT, no matter how many enemies are along with them and try to kill the Dreamrunners as fast as possible.
I'm still playing through DMD as I type, but the above has helped me get through the Dreamrunners on SOS with no problems
- Also, Dreamrunners can kill themselves if they teleport out in the air and fly off the ground