If leveling is a priority Prophecies is just a bad choice overall. Factions is the way to go. You'll be level 20 in potentially a couple of hours; possibly the same amount of time you spent in pre-searing on your existing character. It's shorter, has a steeper learning curve, but aims to get you to level 20 asap (plus you get the option of playing assassin or rit as well).
PS: As someone possibly told you in another thread, grinding levels is a really pointless thing to do. They're really just training levels, so as you complete missions, explore, and do whatever else you need to to get stuff for your HoM you'll be leveling anyway.