On a more serious note, maybe make monthy quest for lower instances(fb19-fb79) that arent used much, maybe like 10 - 15 ec per instance run, 50 ec at completion of all instances under 79...
OR
Make the bosses in the lower instances have similar drops to the tt boss Shauk-Aranos in pv 135+
Because then people would run the lower instances, and it would be easy ec+recraft stones would be nice too
Maybe scale ec drops off tt boss 110+ for fb 19-51, 125+ for fb51, and 135+ (with recraft stones) for fb69+.