Not sure if this is intended, or a bug, but today when I cashed the quest in, I only got gold and experience for 13 chunks of meat, even though I had more than that in my inventory. They all disappeared, though.

It is entirely intentional.

I had much more in my inventory this morning and got xp/gold from all of them, or at least definitely more than just 13x5 gold. Does it work selectively?

*bumps in Thrawn's direction*

Will EFUQS have any effect on this?

EFUQS will have the following effects on Rat meat (and should already be having these effects:

1) A single character can only turn in Rat meat once per reset. 2) Rat meat is worth 3 gold and 3 xp each. 3) Gobbler will only pay for 25 pieces of meat from a single person. (The xp will be likewise capped.)

So, this is fixed?

EDIT: Looks like it is.