First of all, its best to find mobs that are stationary. Some maps have small villages with guards posted at entrances to places, you should keep your eyes out for these are they are perfect, but often quite afk farmed. Once you find somewhere, I would watch how well your eidolon does against it over the space of 5 minutes in case its too much for it. I would also suggest sitting while you do this to stop those freaky people who like to report others for afk farming ;) To make sure you're farming the correct scrolls, just select the mob and on their health bar, press the small chest at the end to get a full list of loot that drops from that mob.
Only certain Eidolons will auto attack back though, all bard class ones will do it (because of you losing health they will heal you and go into combat). You'll have to experiment with this, but if you have the envoy skilled named "Prickliness" then that will have the added bonus of making all eidolons work for AFK farming. The reason for this is that when a mob hits you, the thorn damage sent back to the mob counts as you hitting it, and will force the eidolon to join in. Neat huh? ;)
Happy AFK farming bud :) Hope this answered all your questions.
