Watching my roomates raid group, took them forever to clear E1S, half as long for E2S, and pretty much cleared E3S in a few hours.
Its possible they were all just really rusty, and suddenly are good, but im inclined to think each floor isnt set up to start off easier, and grow harder, but are roughly equal in difficulty, with only the smallest difference in difficulty.
(Could be wrong, havent bothered trying savage this time. I just dont really enjoy half the changes to jobs.)