This is how I leveled in the beginning...
I leveled legitly playing through the game and doing baal runs in norm and nm. Then at around 72 I started doing pit runs and questing through Hell. Then Frenzey and some sorc came and helped my group get to act 3 with them and from there we got to act 5 hell, but stopped because we thought Ancients would be too tough, so I began to level by doing Diablo for other groups and a little bit of the Ancient Tunnels. Then I get word that my friend has beaten the Ancients, so I try to make my own Ancients game, and eventually succeed. After a long battle between the Ancients and my group (a couple barbs, a trapsin and a bunch of cold sorcs), I was 82, the highest on the ladder. I started to do Hell Baals, which were very slow and very dangerous and very scary. Then I died. It rocked.
So anyway... Maphack definitely helped the process, but if our early legit group had stuck together for the first 24 hours and no one died, I'm sure we could have been close to 80 and working our way through act 5.