I play only with rested bar. Not a problem actually, since I play quite casually : if a group is at 70 with full "blue" bar, it will keep it 'till 80.

For the rest, to avoid getting bored, I alternate play styles, switching groups depending on my mood :
- Few days doing mostly quests and gathering mats on my 4 x Hunters + 1 x Druid group (actually at 80 now)
- Few days on my Paladin + Shamans groups running instances
- Few days on my 5 x Arcane Mage group mashing my Arcane Explosion button and laughing at how many mobs I can take down at once with 5 squishy gnomes
- Few days on my real holy trinity group (Pala+Priest+Mage) figuring out the next level of macro complication
- An afternoon levelling crafting skills
...

Levels go up, slowly (casually) but surely (efficiently I hope).