valve collects statistics, yes. Are they used? Who knows, there's hardly any transparency in the balancing process. I will say that Icefrog has (supposedly) been in charge since WC3, back when there was no conceivable way they could have collected meaningful statistics..

I also haven't seen definitive sources about consultations with top players. I've heard about bouncing ideas off pros in the distant past, but not with any regularity, and not recently.

"Better balanced continuously with time" is pretty subjective..