I used to play world of warcraft and questing alone always gather more experience unless it's a group quest. The split exp seems to slow down my leveling, but it does make questing alot faster and I also get exp from the quest. So, which way levels faster? Questing alone or with henchmen?
Have you even played the game for at least couple of hours or research on the internet before you asked this question?
To answer your question; no. Quest rewards are fixed such that party size has no influence on it. You NEED henchman/heroes to progress through the game no matter how good you think you are; this game highly emphasize on team play. People rarely solo through areas unless they are farming for particular items (read it up just in case you are confused)Lastly, 'leveling fast' is highly redundant since you will reach the max level 20 quite easily by normal playthrough.
I have to agree with Pizza. When you start a character in Factions or Nightfall, you can EASILY.... EASILY get a character to level 20 (with out dying I might add = Survivor title ) In under 5 hours of game play. But that's if you know what you're doing, and aren't slowed down by cinematics and mission retries ^^.
Also - Henchman aren't there to be Substitute Party members (even though that's their exact purpose, they don't come even close to having some one else on your team) All they really do is provide minimalistic assistance, up until the henchman are level 20, in which case - they're pretty dandy. Often times, the henchman AI will operate on a much higher level of skillful play than a new player, so for lower level gaming - I highly recommend a group of Heroes and Henchman.
Contradictory to that fact however, is the always irrefutable proof that pro players trump all.