I have made good progress pulling four of my toons with one 70 from 23 to 40 now, in hour per level or so, first in the stockades, then in SM. I think the key is to look at the XP formulas. You get Ok-ish XP while the mobs are between your level and nine levels ahead. This is with a 70 in the party lowering your rates.

of course the question is if you want to play your team pure or boost yourself =]