Hunts, built in wait time.

[Kinseykinz]

The 'pull' mechanic does not need to be changed. It is working as intended. Which is to say, if you find it, and do enough damage (well actually generate enough +emn) you get credit. So there is no reason to make it so mobs are immune for 'x amount of time' ...and this by the way, even if implemented would solve nothing. People would STILL whine about pull times, and STILL whine about getting there too late and STILL whine about solo players/groups who honestly find said B ranks and pull them w/o announcing to the server the mob is up. All it would do is postpone the complaints for 3 minutes.