With Elemental Evil's level cap increase, Cryptic decided to boost all the old level sixty endgame areas up to seventy. I had to think about this for a while, because I'm not against repurposing old content in principle. I do however think that in Neverwinter's case this has not worked out very well for a couple of reasons:
1) Considering that the quests for places like Sharandar still pop up at level sixty and that the game offers (somewhat ineffective) level scaling, casual and returning players get suckered into thinking that they can level up in those old zones and get trounced as a result, which causes them to leave in frustration. (I actually had this problem myself to a degree.)
2) With effectively no old content left at sixty, the only way to level up by questing is by doing the new Elemental Evil zones. This means that players are funnelled into what's currently probably the worst content in the game, and may - again - cause them to leave in frustation.
3) Even for those who can cope with the new level 70 versions of the old campaigns, playing through nothing but the exact same content that they've done before just to get a couple of new rewards is bound to get boring quickly.
Also, it simply feels tedious when mobs that you used to be able to beat quite easily are now so much stronger - especially when your character is the one who's supposed to have gained power. My pet tank and I did two rounds of Icewind Dale this weekend and what used to be a fun little romp left me feeling tired and exhausted. While we never died, it took ages to kill anything, and since the mobs were so deadly, complete focus and constant dodging were required at all times.