actually I have to disagree with the fact that you must start a new char for each storyline just to get more quests...
It's very pointless starting a NF Necro when you already have a Necro from Prophecies why?
1. You won't have any skills and will have to recap all the skills again

2. You have to do all the pointless n00b quests in Istan just to reach a certain level and get enough sunspear points to proceed further
3. You lose one character slot from creating two identical characters.
4. You'll have to travel back to prophecies and redo the missions that give your characters the necessary skills otherwise you'll have to PAY for every skill you want to buy and quiet frankly once you reach the 1 platinum mark for a skill it gets rather expensive to buy over 100 skills/sig caps etc.