Since you have a 70, do what I like to do sometimes. It's a little more work, but it turns out better.
Instead of using your time to grind out lvl 55-60 mobs, even in an instance with elites using your 70, grind the normal things that the 70 grinds. From the sales of those mats, even though you need some later, buy the illusion dust off the AH. Chances are, the mats you are selling from 60-70 items is worth more than the illusion dust.
Ie, you spend the same time grinding for more profitable mats. In this case, you're just about to need the next tier mats also, so you can start building up the supply.
This is similar to people who would go grind rock elementals for motes of earth. At the time, motes of almost anything else were worth 1-5x as much as earth. Good for them, but I would farm motes of anything else, and sell them, then get 1-5x as many earth motes from AH for (a little over) the same time spent.
Edited, Jan 24th 2009 9:47am by bluegayle