Maro basically stops paying attention to sets by the end of Development, and feels almost completely divorced from discussions on power level except when he's talking about how the entire team almost got fired for Urza's Block.
With regards to that guy's question or comment that Maro was responding to, Wizards does do a bunch of surveys and market research. Their big problem, or at least my impression of it, is that they don't do a proper job of trying to correct for power level's entanglement with the other aspects they study, like art, flavor, settings, or mechanics. Kamigawa is like bottom of the barrel in everything including art/flavor/setting, which seems nuts to me. People like things that are powerful, and liking them for power level taints how much they like everything else about the card or mechanics.