Proximity agro and mobs fleeing.
 

I was pulling blue con Iksar mobs to a ramp in FOB and all would flee at 20%. Another player pulled an identical mob right beside me and engaged. My mob didn't flee at 20% - neither of us were grouped. He took off after that so I didn't get a chance to test this. Is this right or have I been soloing too long away from others like some weird hermit?

Edit: mob did not flee at all, acted like undead.

If more than one mob is aggroed close to each other they do not run.