it all depends on your playstyle. if youre in plate you shouldnt be rolling around for starters.
As far as leveling goes, I just restarted a new character 2 days ago and with 10 hours played ive gained well over 55 levels. It shouldnt be slow once you know what youre doing

Yeah if you farm the the pre-boss section of 4-1 you can get yourself the much needed head start, go tear through some worlds, then come back and farm through 4-4 (maybe 4-3, been a while) that should pretty much carry you through the game aside from a couple of optional bosses. The game actually becomes incredibly easy once you learn all you have to do is play it like zelda but a bit more cautious around ledges and groups.

Also firestorm more or less breaks the game