Multiboxing 85-90

Hi Im lvl 84 and I was worndering if anyone has any idea what the fastest and simplest way of lvling a 4Dk and Shammy team is. Grinding mobs? if so where?

I found that just questing was really the easiest.
With 5 toons each quest is remarkably quick.

[Ualaa]

You could do LFD, if your team can clear dungeons.
The Brewery dungeon is an option, even if you just clear trash and repeat.
Because it is LFD, you can do the trash in a few minutes, leave, disband, reform and LFD again without a lockout.

If you're on a PvE server, questing is always good.
A quest stacking guide makes it more so.

You can also PvP.
Random Battlegrounds get you bonus Honor.
And any objective/bonus honor earnt, is extra experience when not at maximum level.
If it's AV or IoC weekend, queue those games instead of Random.