leveling 60-70 is going to be pretty easy because the reduced the XP requirements to level in this range, I only do 3 zones such as hellfire, zangarmarsh and nagrand and i'm usually at 68 or so .
I suggest Borean Tundra @68 since most of the quests in that area are Melee friendly quest rewards ( DK, Hunters, Rogues will love the rewards here )

You will feel like you hit a brick wall at 70 because the XP requirements are much more than anything previous.
So at this point you are probably going to want to only level up your most dungeon viable team.
for me personally a tank, 3dps and a healer is probably the most viable.

The druids can do this without help from other classes.
The good part of druids is that they can rez the fallen and even do battle rez.
And to top if off the DPS druids can heal in a pinch.

I say mix it up, a DK tank, a druid healer and possibly other druids as DSP or use any combination of DPS that you have.