ok from here -
http://www.angelfire.com/games2/eqfo...ruid.htm#snare
it says "This is probably the best facet of snare. When a mob is low on health, it will start running. At lower levels, this isn't a big deal, as you can kill a running mob with a few hits. However, at higher levels, mobs will start running earlier in a fight, and it will take a lot longer to kill them."
could be higher level mobs are supposed to run earlier, therefore not stopping mobs at the required percentage to stop them when an otherwise lower level mob will run later already after the required percentage to stop them