My opinion: Lead has primary responsibility for sorting contacts. He needs to pass this off if he is heads down or otherwise engaged. Rest of flight attempts to sort around lead's sort. If they can't, they must TELL lead so lead can change his sort! Lead needs to flexible about sorting, and the rest of the flight needs to take initiative in sorting and COMMUNICATE!
Check this out. It's from Raptorman at Frugal's world. Best method I've read for sorting contacts.
"If I'm in a multiship BVR engagement and lead is sorting targets, what do I do if I can't sort mine?
First of all, communicate this fact.
Cowboy 1-1 Contact, 11 o'clock, 40 miles, angels 15.
Cowboy 1-2 Confirmed.
Cowboy 1-1 two contacts, 11 o clock, now 30 miles, one lead, one trail 4 miles behind, both angels 15, sorting the lead bandit.
Cowboy 1-2 not sorted, negative on the trailer, sorting the lead bandit, 11 o clock, now at 25 miles, angles 15.
Cowboy 1-1, roger your sort, targeting the trailer, 28 miles, angels 15.
Depending upon the targets range, there's a window when targets can still be sorted and bugged/locked around someone else’s contact prior to firing. You still have time to do something about the failed sort in this situation.
The contacts will have been called out and you should know where to look. Check your HSD in the right MFD to see bugged targets that the rest of your flight has sorted. If you see nothing on radar, the only thing you can do is to turn your radar in that direction and try to get a contact. Support your lead while you attempt to do this.
If you have a radar contact but cannot sort, then bug a target and inform lead. The rest of the flight can attempt to sort around your lock.
You should establish a minimum range at which any fighter who remains unsorted will simply lock into the bandit group and fire. This will be prebriefed, but 20 miles is a good number. Do not wait to be told to do this. If you are weapons free, FIRE."