If you can afford flying mounts, questing is ridiculously quick and easy in Outlands.
If you are on your 2nd team (or later), add in two heirloom items for an additional 20% boost.

Not to mention, 1st to 70th only requires 70% of the original experience per level.
All mobs and quests give 30% more then they used to, when that was current content.
Which with heirlooms is half the original time.

I'd quest, skip collections unless the item is lootable by everyone or the kills are fast/easy.
You can instance a little if you like, but quests will be faster.
And pvp is an option, but again I'd probably wait until 71+ or better 74+ before adding that.
At 74, 5x toons can contribute quite nicely in AV's.