If you're asking if they take low elo in mind for balance, not really, and there's no reason they should. They'll make some adjustments if something is way out of line in low elo, but in general for every game it makes sense to balance at the top.
Player skill in low elo varies significantly, so player skill matter a lot more than champions or items. Someone can climb to diamond playing nothing but soraka ad top.
However in high elo, champion strength matters a lot more as the general skill level is a lot more even. If everyone plays everything to its highest potential, you'll get a much better sense of what's objectively too strong or too weak.