Your post isn't entirely correct or honest.
Every so often a battle mage will hit 15-25 damage in one given hit, granted it is rare but it does happen.
Another thing, if you are afk for 24 hours how would you pick up the drops?
Sure you can afk there - but, trident only has 2.5K charges, so does a slayer staff. If you fancy bringing a big risk of runes into wild (not sure if you risk w/ rune pouch, think you do) then last as long as you like, but you still have a chance of losing all of your loot to a PKer when you run back to mage bank.)
PKers operate a lot too in the area and you can eventually get the battle mages off of a player to kill them.
But they do, do very little damage and I often see people getting X amount of drops throughout the day wondering if they are entirely AFK at the mage arena. If they are, feel free to go PK them.
Their drop rate is also pretty low for the good items, all the wands prior to teacher are junk and they are most common. (I know you can exchange for points, but 100/200 for beginner/apprentice wand)
Maybe just add to their accuracy, people barely use the battle mage spot as it is. Maybe a couple of people at maximum at one given point, so wouldn't want to scare the people away that use it to make some money.