I was going to write out a big old post as to why 2.55 is a dumb requirement for heavesward, but I decided to save myself some time and just write a short version of it! lol.
Simply put, the main scenario quests up to 2.0 flow very well with leveling, but the level 50 stuff is very long and tedious. While it is true that if you sit down you can grind it out in 6 hours or so, I feel that people will have less patience for this at expansion time when they want to go to the new zones. As a result I think some players who are working on the questline may get annoyed with this chore, lol. That could make them want to stop playing.
There are two types of players who will be grinding level 50 main scenario quests at expansion time:
Old players who didn't do it: Players like my friend who fate grinded 3 different level 50s is going to have to go back and do it. This is going to be a very frustrating chore for him since he does not like questing. Granted I don't feel to bad for him since he has had plenty of warning, but it still sucks and I wonder if he will continue playing.
New players: The main scenario quest is going to work well for new players up till 2.0. After that the quests are going to be a grind for them. While they will probably add xp to the story quests, I think some new players may become discouraged when they level up to levels 53 or 54 and still can't go in the new zones. Granted everything is "new" to new players, but I have played other MMOs and I know that new players generally want to quest and level in the highest level zones they can. This level 50 story quest gate is going to make a lot of them feel like they are being held back.... and that is not a good thing. I want the game to grow and the last thing I want is for new players to quit because they feel like they can't advance to the new zones.
Anyways, I truly believe that the 2.0 questline is good, but I really think they need to re-evaluate the 2.01 to 2.55 requirement for the new zones.
And before anyone says, "It does not take that long", you are right that it does not.... but...... and a big BUT.... It is going to feel like forever to someone who just wants to walk around the level 51+ zones.
EDIT: Thought Id add before I get any more dumb replies about "making the game easier". This is not about the game being easier. This is about a smooth leveling transition from level 50 to 51 for new players. Right now there are to many level 50 quests in the main Scenario and it won't be a smooth leveling experience for new players. New players are going to feel held back when they are hitting levels 53 to 54 and still on level 50 content. That is the problem.