Well I didn't say anything about 4x30's but the point is that you can't do LFD if the toons are of wildly different levels. If you are lucky enough to have a near-level toon on the boosting account then you can form your random LFD and have that toon leave the group after porting in and then invite your level 80. You can still clear the dungeon and get your random loot bag at the end!