I don't remember where the option is...but someplace in your settings you can switch it so that grey quests still show the feather icon above quest NPC heads. So you can easily go back and do old quests.
I was in your same boat, I came back to the game a long while back and alot of my characters had next to no AA's. I deleted them all. lol I did try to play catch up on one but leveling is so fast now it took me no time at all to get back to level 50.
***EDIT*** I dug around till I found the option. Go to options/User Interface/Name and Chat Bubble then scroll down and check "NPC Overhead Quest Icons for Outleveling Quests." 