The ability in question:
At 4th level, the pack leader learns advanced techniques for fighting as a group. As a standard action, the pack leader can add up to his Wisdom modifier in creatures into his pack, which functions like the collective of a tactician with a class level equal to half of the pack leader’s ranger level (round down), but the pack can only have a maximum number of creatures equal to the pack leader’s Wisdom modifier. The pack leader does not count against this limit.
When members of the pack are attacking the same creature, they gain a +1 bonus on weapon attack and damage rolls against that creature.
This ability replaces hunter’s bond.
Bolded for question.
How does this work? Do we have to ready actions to attack at the same time? Do we have to be threatening the same creature or merely be able to make attacks at the same creature? does one of the pack have to have made an attack before the bonus can be used? Do they have to hit? Does the 'I count as my own ally' rule apply? How long does the pack get the bonus? If I made a potshot at a recurring villain that one time, does the pack continue to get the bonus versus him until we kill him?
My interpretation would be that you get the bonus so long as a pack member attacked the enemy since the last time you attacked.
So, say you have 3 pack members and 2 enemies.
1st round
Pack member 1: Shoots a single arrow at each enemy, getting no bonus.
Pack member 2: attacks enemy 1 and gets +1 to hit and damage
Pack member 3: attacks enemy 2 and gets +1 to hit and damage
2nd round
Pack member 1: Shoots a single arrow at each enemy getting a +1 to hit and damage for each attack.
Pack member 2: attacks enemy 1 and gets +1 to hit and damage
Pack member 3: attacks enemy 2 and gets +1 to hit and damage
My interpretation would be that you get the bonus so long as a pack member attacked the enemy since the last time you attacked.
So then, round by round? That seems like a tracking nightmare.
Unless you're changing targets a lot I don't see it being that hard to track.
If you feel that you need some way to physically track who attacked what, just assign a unique color to each pack member. When a pack member attacks an enemy you stick a colored pip,disc, whatever on or next to the enemy to mark it. These are retrieved/removed at the start of that character's turn and redistributed as they attack. If a pack member attacks a target that has a color on it that isn't their own then they get +1 to hit and dmg if not, they don't.