If by starting over you mean starting a new character, then there's really no need to do that.
MSQ's give you a lot of EXP but it's not worth the hassle of... having to go through the MSQ again.

The only part of PotD that's worth doing for EXP, is the 51-60 stage. You just want to spam that.
Generally you want to just spam your latest leveling dungeon (e.g. levels 18-49, 51-59, 61-69, etc.) and this is typically your best source of EXP, but of course DPS wait times can sometimes make this prohibitive, so that's when PotD comes out on top.

That said, while you're waiting for your dungeon queue, you can always do your daily beast tribe quests, and grab any EXP boosted FATEs you come across, and all together this could beat out PotD for EXP gain.