This doesn't seem right. Either I'm misunderstanding what you're arguing or you're claiming that a deck full of farming villages is equal to an identical deck of regular villages. That can't be true.
Take a basic deck of 10 coppers, 5 estates. Now add 5 farming villages. If these were regular villages, your deck would not improve. (In theory, by manipulating shuffles you can actually beat the odds slightly.) You will draw your deck, worth 10$, every three turns. However, farming villages muck that idea up. Since you have a chance at skipping over estates, you will actually be drawing through your deck faster than that. Potentially, you could improve your deck to the point of drawing 10$ in two turns, not 3. That's a significant increase.
Every time you skip over a dead card in your deck you are playing your treasures at a faster rate than you normally would. You're not magically making your future draws better, but your deck is obviously better for it. If you switch out farming villages for ventures the results are identical.