Garthanos
Arcadian Knight
Yes, the mob rules are a decent way of making a group of standard 1 HD creatures an encounter that a mid-level 3E party will pay some notice too. Under RAW a couple of score goblins would have trouble even scratching many 8th-10th level characters.
I prefer the Dungeon #113 version were mobs can have different Hit Dice. The DMG2 one were all mobs have 30 HD doesn't seem right.
Sounds too inflexible 4e has examples but I would have like to have seen more. I think the idea actually needs more development.