We could use a Preferred/Blocked player list for DF.

[chocomaid]

As positive the idea is, it would be very difficult to implement.

Imagine:

A - You
B - Player you liked (on your pref list)
C - Player you Blisted on your blist

It will be very difficult to make a system that will recognize and calculate all these variables. Imagine if you (A) and B queued at the same time and are on each others' pref list, C queued at the same time as well, but C is on the pref list of B but not you. Who will the system prefer and such. And that's the simplest of examples. Imagine a dungeon with 24 people, preferring and blisting each other. You'd never get a raid to form at all.

A different suggestion that might benefit with this positive way thinking regarding DF is the ability to re-queue as a group at the end of the instance run, assuming that you all liked playing together and have time for more!