In order to do this, you have to make T1 dungeons worthwhile. If you run T1 and KNOW that the item you are going to receive is inferior to a T2 item and will probably sell for maybe 10,000 AD max on the AH, there's no incentive to run (unless you're going for stalwart helm or something like that, with a low drop chance).…
I fully agree with this point. However since many players' main source of income is the loot from dungeon runs (if they don't want to grind foundry/pvp or don't have lvl 20 leadership already), they often feel that a run where everyone wipes before the boss is worthless, especially during DD. Perhaps scaling up skirmishes…