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Took me around 2 days (of playing time, i.e. /played) to hit 60 with a TR (I know, I'm terrible). I can't say that rushed...really.. All I did was play through the base quest content casually and do a few foundries for the daily ADs.
Without the foundry the content in this game would be trivial. With the foundry, it still lacks end-game content; there is no significant tie in between the foundry and the best gear in the game yet.
I think it behooves cryptic to let the player base design the end-game dungeons with moderated content (to ensure no more "ogre push" exploits).
Foundry quests are definitely sort of the novelty factor to this game, but once you hit 60 they just become a daily chore for AD as you get no other reward (once you're in level 60 greens).
I'm not going to make any ridiculous claims like the population is taking a nose dive, but you can see different metrics that indicate the standard down trend for a newly released MMO and unlike many MMOs this games leveling curve is almost a straight line.
There are no alternate quest paths, no different starting areas, few classes (they are obviously in the process of adding more, but the same content is the same content at the end of the day) and very trivial character progression.
They could make leveling a lot harder, sort of forcing you into the foundry, which wouldn't be that bad of an idea, or they could tie in the foundry better with end-game content.