There are ways around it. Here's just a few:

1) The rescue thing you mentioned. I reported this being abused when a necro used it to rank/spam sleep on mobs about 30 levels above him in a certain dark city. Imm in question didn't seem interested in checking it out, and just said something about let us know if it happens again. Interestingly, whilst I can't remember how it happened, the lowbie necro got one of my groupmates killed by releasing his golem when we tried to kill the mobs so he'd leave, and full-looted him.

2) I've killed undead ones before by letting my zombie tank the undead, whilst I fought a fairly weak mob, and spammed disrupt on the undead, with occassional vamp touch on the weaker mob. You can kill some of the strongest undead in the game like this if they have defilement attacks.

3) With auto assist off, I had zombies rescue me in Thar-Acacia, then spammed blind whilst not in combat. This enabled me to rank solo without resting for 500 exp per kill.