I'm not sure about the pet boosting, but I couldn't make it work back then ^^... Even if it would work, I'm not sure if it would be worth the effort.

I've found a much simpler method - that's if you've got a druid.

Thorns - As most of you know, you can't apply high-level-spells to a low level toon such as lifebloom. But the great thing about thorns is, it scales with spellpower (since 3.1 or so). I reached about 4.1k spellpower on my druid using an on-use spellpower trinket. The result was fairly awesome, 150-180 backlash damage on level 1-20. Meaning: After being hit twice, the mobs die.

If you combine this knowledge with the instant-mob-respawn locations, such as the crabs in Westfall or the Worgen in Duskwood, you can endlessly pull mobs and level at a ridiculous pace, let the druid do some healing - out of party of course. (note: Nourish rank 1 can be casted on low level toons and still heals for about 4k... But Rejuv and Regrowth are good enough generally)