Hitting level cap can be very daunting and quite depressing. I know both me and Ooga hit level cap at roughly the same time and I think we both went through a few different stages of just simple not playing or only playing our mains and not multiboxing.

Your so focused on pushing to 80 that when you arrive you suddenly realize the game has only just begun and you have a huge list of things to do.

I would suggest perhaps creating a google docs spreadsheet and writing down a list of things you need to get done and what you need to do to achieve them. For heroics you will want a tank but you dont necc need a seperate healer. I use a paladdin and 4x shamans and its no problems other than that I can be quite horrid at instances.

Get crafted saronite pvp gear or go do some ice crown and storm peaks quests to get some decent blues. Look into faces of doom offhands and titansteel guardians.