The 60 to 70 process will be a lot easier, with a 30% reduction in exp per level.
Not sure if collections can be entirely avoided here or not.
Or at least the painful ones skipped.

I don't believe we can level from 70 to 80, via quests and avoid all collections.

However, some collections are less painful then others.
Especially if every member of the team, via Interact, can loot an item.

It will probably be a rather large project to put together a 70-80 progression.
One which is boxing friendly, I mean.
There are a few guides for 70-80 out there, but they're from a one-box perspective.