Dan wrote:
The downside is, you need lots of them, after the Ring of Recoil deals out a certain amount of accumulated damage, it vanishes. I don't know how many you need, I have never done it, but I have seen it been done

if i recall right it does 10% the damage you receive back to ur opponent but only up to 40 dmg then goes kaboom.
as for being able to kill them before, back when the swarms were first out you could dmg them with fire spells, but they were made totally invincible not long after they were made. and since then the only way to even damage it has been a recoil ring.
making them not be able to be attacked was to let the auto-log out feature activate when auto-ers, or afk'ers, stop fighting everything else around them for so long. hopefully jagex adds poison to them soon to really get rid of alot of bots.