New level progression 'speed'

Before Act4 was added, when someone said they fought (say) Dominus at level 56, you knew they were in Merciless.

I'm reading a forum post, and this dude wants help with his level 61 toon. I have no idea where he is in the game.

Further confusion is that I tried my best but once I (barely) got into Merciless, I was really over-leveled. I think I hit the Strand (Merciless) at 63. So I have no idea what 'normal' is.

If people could list approximate levels they got through the various acts at the various difficulties, that would be helpful. I'm not looking for people boasting here; ubers are out-layers and unimportant in this context.

Well, it probably varies quite a bit from person to person, but for my part I try to match the zone levels as closely as I can, to not have any drop rate penalty, so my level is the one of the zone I'm in, plus or minus one. I'm in A3M for the moment, and I haven't had to grind at all yet. Also, I should say, I'm not a particularly good player, I just follow builds that look cool and affordable.