Recently did some interesting ATC simulator training. We sat with out backs to the screens until the Short Term Conflict Alert went off (10-20nm before returns merging) then turned around and tried to fix it. This is not separating, it is collision avoidance when separation has failed. Brilliant fun, but unknown realism, with the blip-drivers reacting immediately & turning the right way most of the time.
How to do this has changed with the advent of TCAS. An excellent CAA (UK) manual on the subject (which I have forgotten where I got, but was available on-line) suggests "leaving the vertical" to the TCAS to sort out, with ATC input restricted to headings, unless a full vertical separation standard (less likely to set off a TCAS) could be maintained. (My paraphrasing.)
These techniques are not documented anywhere, as yet, in our (Australian) manuals, and not everybody I work with has yet undertaken this training.
For every pat solution developed somewhere there is a reason it will not work somewhere else. Nothing I have said should be taken as a critisism of anybody. I will wait for the outcome of an investigation before I offer any opinion on this accident, but would encourage ATC everywhere to try these techniques and situations first in the simulator.