Are transiting planets with TTVs being discarded?

Potential Biases in the Detection of Planetary Systems with Large Transit Timing Variations

This paper suggests that systems with significant TTV should have been detected by ground-based programs already, before the discovery of Kepler-9 and Kepler-11. Perhaps the reason why they haven't is because the algorithms used to process the light curves are too optimised for regular periods and thus discard the candidates with substantial TTV.

That's the fun thing about experimental science, there are always biases.