I noticed a similar "bug" today with my priest/4x hunter group. I had Aspect of the Pack active on all 4 hunters and yet the priest didn't get the benefit of the buff. I stopped, swapped aspects on all hunters, then swapped back and had the same problems. No latency or range issues to speak of, just didn't gain the benefit. Not sure if it's related, but it was very weird. I haven't dug into any of the Bliz forums either, so it may be a known issue.