If you have a healer then have the healer not group with the dk and just have it follow dk. I was lucky i had a 60 healer so when i got my dk to 60 i just grouped with the 60 for outland quests and it was a joke. The dk gear is so op for outland, i think i only upgraded 3 things and that was it. Have a healer with you means no down time. DK is sort of like a warrior with rage bar, the less down time the better. So if you have a 60 alt healer then group (think it took me 3 x 6 hour days to get 60-70). If the healer is 70 when just follow and spam heals when the dk needs it.