I think it would be better like this:
1. A new player has to play all 3 difficulties to have an easy start and getting used to the difficulty. Only when a player has finished all difficulties, he has a new option.
2. When a player has finished all difficulties, he may enter the "Alternative Merciless" difficulty when creating a new character. In this difficulty, the player has -60% on all res right from the start and the level of each area increases much faster. Example:
Act 1:
- Twilight Strand: Map Level 1
- The Coast: Map Level 4
- The Mud Flats: Map Level 6
- The Submerged Passage: Map Level 8
- The Ledge: Map Level 10
- The Climb: Map Level 12
- The Prison: Map Level 14
- Prisoners Gate: Map Level 16
- The Ship Graveyard: Map Level 18
- Mervails Caverns: Map Level 20
Act 2:
- The Southern Forest: Map Level 22
- The Old Fields: Map Level 24
- The Crossroads: Map Level 26
- The Chamber of Sin: Map Level 28
- The Broken Bridge: Map Level 28
- The Riverways: Map Level 30
- The Western Forest: Map Level 32
- The Weavers Chamber: Map Level 34
- The Wetlands: Map Level 36
- The Vaal Ruins: Map Level 38
- The Northern Forest: Map Level 39
- The Caverns: Map Level 40
Act 3:
- The City of Sarn: Map Level 41
- The Slums: Map Level 42
- The Crematorium: Map Level 43
- The Warehouse District: Map Level 44
- The Market Place: Map Level 44
- The Battlefront: Map Level 45
- The Docks: Map Level 46
- The Solaris Temple: Map Level 47
- The Ebony Barracks: Map Level 48
- The Lunaris Temple: Map Level 49
- The Imperial Gardens: Map Level 49
- The Sceptre of God: Map Level 50
Act 4:
- The Aqueduct: Map Level 51
- The Dried Lake: Map Level 52
- The Mines: Map Level 53
- The Crystal Veins: Map Level 54
- Daressos Dream: Map Level 55
- The Grand Arena: Map Level 57
- Kaoms Dream: Map Level 55
- Kaoms Stronghold: Map Level 57
- The Belly of the Beast: Map Level 58
- The Harvest: Map Level 60
Act 5:
- 1. Map: Map Level 61
- 2. Map: Map Level 62
- 3. Map: Map Level 63
- 4. Map: Map Level 64
- 5. Map: Map Level 64
- 6. Map: Map Level 65
- 7. Map: Map Level 65
- 8. Map: Map Level 66
- 9. Map: Map Level 66
- 10. Map: Map Level 67
People who start in the alternative Merciless difficulty can also go to normal, cruel and merciless difficulty, in case a new player wants to interact with someone who plays alternative merciless. Also you can't do quests from the other 3 difficulties once you have started alternative merciless. The advantage though is, the the quests now reward you with all the things from all 3 difficulties. So if you kill fairgraves the first time, you are rewarded with a book that gives you 3 passive nodes instead of one. This way, you only have to do the quests once. When you do the bandits, the guy in the town will give you all 3 rewards. And thanks to the rapid increasement of map levels, leveling at the start goes much faster. And since you start with -60% resistance, the early game should also be much harder, since bosses like mervail will hit very hard because you will probably not have capped resistances in the low level area. Furthermore, you only have to do the labyrinth once to get the first 6 lab points. Especially nice for those who dont like it anyway.
All in all that means:
- You only have to do the storyline once per character
- You only have to do each quest once for the important quest rewards
- You only have to do the lab once (except ubber, still needs to be done)
- The early game will be more exciting, since you start with -60% resistances at level 1 and level from enemies increases very fast.
That would solve the problem of doing the same thing over and over again in a boring context (because normal/cruel are to easy).