Having reached 60, with alts at various points, I became able to give my refer-a-friend an instant level 60. Well, instant would be pointless: might as well create another alt myself and run through the newbie town, because that gets you to level 9 (with triple-xp) in less than an hour. Might as well save those granted levels for when they’re worth more.
So we made alts and quested our way to Goldshire. The next time we got together, he thought it would be fun to play those characters again, so we did most of the Goldshire quests. That, plus running to Westfall for the gryphon (plus some minor violence along the way), left us at level 14. Turning in any quest yielded multiple bars of xp.
That almost caught up to the first alt from whom I was going to start granting levels. That is the Mage, painfully leveled solo with the pitiful mana regen. His Mage reached about the same point in a coupe nights of easy grouping. He hasn’t even twinked this one, because it has not mattered: it goes too quickly, and who needs to farm more heirloom gear when level 60 is right around the corner?
I like my shiny new level 14 Rogue. Woo! But it makes playing solo kind of pointless. I would be better off dual-boxing, putting a character of his on /follow, and getting more rewards for everything I do. Which I have done, when there was a level-relevant character available. If nothing else, summoning a friend to a quest hub for an effectively free level at quest turn-in is nice. But it does make playing without him seem like a waste of (2/3 of my) time.