If the farmers are doing anything, they are supplying the market with Influence distribution. Since I've returned to playing, I've made not even a single character 50. It's not all the interesting to me to be 50 to be honest. One of my toons is a level 5 Emp locked with xp turned off.
I've had no problems making money.
In general I make 7 influence per minion
I have made about 250k from teaming.
I have made millions working the market though.
I've been crafting for the badges, I'm working on level 45-50 IO's and I'm level 5!
So, with that in mind I'd simply ask the question, What is balance?
Certainly my level 5 does exceedingly well alongside players of all levels with my stacks of temp powers and slotted with SO's that give me fair percentage and decent returns on a character that is only a month or two old and not consistently played.
Thus, the minor change to influence when xp is turned off is nominal in my opinion. I don't think the change will impact the economy all the much to be honest.