"Right now I have 3 active accounts, 2 of which have a lot of characters 60-70."

"I just dont want to waste the time and effort into lvling a third account if theres no point."

Why not transfer some of your high level toons to the other account(s)?

This is exactly what I did. I had a hunter who was level 66 and I wanted to dualbox with my 70 Priest. I just got a second account and transfered the hunter over. If you've already got a good bunch of toons, you don't have to level more.