The thing is, this used to only effect flat worlds, when this first came around. I could still find villages that had a decent balance of farmers. However, it seems that when 1.7 hit the floor, it effected everywhere. 1.8 seems to have semi-fixed the problem, but only in some villages. The balance of villagers still make farmers extremely rare. I'm not sure if at this point it's even a bug, or just an attempt to make a larger variety of villagers at any given village. This bug has been here for over a year now, me being the initial reporter, and at this point I'm not sure this'll ever get fixed. Ah well, maybe one day.
I made this report 4 years ago. I'm still receiving emails on it to this day. I think at this point, "it's not a bug, it's a feature" applies. Mojang is obviously okay with the spawn rates, and I don't think they are planning on changing villager spawns. If this was unintended behavior, I think they would have updated us on this issue by now. I think it's time to let this one go.