Honestly I've seen many people do HM Garuda just fine with full AF and/or some AK/Darklight pieces.
But to the OP: You tell them they should run Wanderer's? Why? A DPS queueing for Wanderer's may as well just queue for AK considering the wait time is still horrid and the drops from Wanderer's are pretty much good for only one thing, and that's converting into materia. Not to mention the amount of farming of AK, CM etc for Tomes of Philosophy for Darklight gear.

A lot of people just want to experience the content, which by all means let them. The more experience people get the better duty finder/PUGs will be.