Just as an observer it seems SE is in a tough position right now. As one of the few companies remaking their game while still having active players they are currently top heavy as far as level count. So for many current users adding in loads of lower level content isn't content to them at all.
But if you just add endgame when the 2.0 new blood will be unimpressed.
The other issue is to say people who have done it won't go help on say, Toto-rak (for a current example) for some, perhaps many is true. Theres a fair portion who helped me, and i've helped. The issue is when you want to do a low level dungeon, and the only people you can find are lvl 50s blowing through the dungeon with you in tow...Thats hardly fun either.
My first tot-rak was with a very nice person who was willing to help me finish the quest. And of course I appritated the help. But the dungeon wasn't what i'd call fun. It was basiclly run behind him, watch things die, finish quest.
When i ran with someone to help after i was only lvl 31. It was very very fun. the fights were actual fights. we worked together.
TL;DR. The current player base is so advanced in level that they are likely to demand more endgame content and instead request others meet them there quickly. New players will need something to do to keep interest while they attempt to get there. And SE is crunched for time with 2.0 itself, never mind large amounts of content for both So my possible solutions:
level "pegged" dungeons: This may be the easiest as far as time goes for the Devs, depending on the code, because it would spare the time of making new Locations and only require them to make a setting and spawn level appropriate monsters and different goals/bosses.
For example AV lvl 50 dungeon, as is. AV lvl 30 version: less to no HP poison gas. Instead it inflicts Heavy debuff. Enemies are instead maybe Puks and Moles. Coincounter is instead big Balloon, Miser is a Large Flytrap.
The added benefit of this system is new players will become more familiar with the dungeon map so when attempting endgame dungeons, the fight mechanics are the main focus of practice.
The negative would be the repetative maps. Personally i find this the lesser evil aslong as the fights and mobs are a different as possible.
I'll pause here before i make a GREAT wall of text, and add more thoughts should the thread continue constructively. Thanks ^^
Oh did forget one thing: Old content can be attractive if 1: Vanity slot or similar system is implimented, providing some reason to go back to content for a personal look or 2: A small reqard, be it seals, tokens to "something" or anything semi desireable but not provided in spades to atleast lure out the helpfullness hiding in all (most) people.