That's kinda dumb. It'd probably be more time consuming since it would be harder. Just approach Playthrough 2 like you did 1 (or I'm assuming you did) and try and do everything you can as your progress. If you just do story missions (which are usually the hardest) you will have a tough time. Do all the side quests (usually starting with the easiest) so you get stronger and go through the remaining quests with more ease. You should be level 50 before you even finish the second playthrough.