Yeah its a bit of a crapshoot right now. The problem is there is no penalty for dropping group. So people leave for whatever reason and requeue. Also if leader goes AFK or DCs, there's nothing you can do but wait or drop group.
There's so much simple stuff Zenimax can do to fix this but they haven't yet. I think some changes are coming with new patch/DLC, but it won't address all the issues with this system.
For now best thing to do if you wanna run a random is group up with 1 or 2 other people before going into Random, this way you're going to get a leader that wont disband/ditch group.