With this little trick, it's possible to increase the levels of a brand new character rapidly. You need a high level character that has finished Legendary (Cazic Thule may be a bit easier, although this works with either final boss). You will also need a two player game. Although you can do this outside of the final boss battle, you can do a bit of farming while you're at it. Start the final battle as normal. If your new character gets killed, s/he will still get the experience from the battle, so you do not need to worry about keeping the new one alive. Kill the final boss like normal and collect all of the goodies he drops, minus the final Innoruuk shard. Once you do that, exit the mission via the Pause menu and you'll be back at the stage select screen. Pick another mission, exit that one and go back to the final boss. You can now repeat this over and over to powerlevel your new character. You should be gaining about a level per kill well throughout the high 20s and low 30s.