Guide to AoE Bard Kiting, here on P99.

[jerus]

Lots of the mobs are pulled with just proximity agro and have very little agro on the bard, so if they have any reason to hate you they may break off their current path and agro on you. Mainly happening when they are kiting the same things, basically you have an Aviak, he has 10 aviak, some of the aviak are only proxi agro on bard they see you killing an aviak, they decide they hate you more.

At least that is how I understand it.