Toaster Loving AdMech Boi
When I’ve used this system, what I’ve done is roll once for each group of mobs that take the same action (or category of action). So, one roll for all the enemy archers, one for all the enemy casters, one roll for all the enemy melee combatants. I prefer not to add an extra die for movement, so that hasn’t been an issue for me. I suppose, if I wanted to add that factor in, I would have them move or not move in groups - either the enemy archers all stay in place, or the whole block takes the penalty so the units have the option to move if they need to.
Yep, that aspect of it is pretty easy to handle for any DM who is already experienced with handling larger scale battles with lots of mobs. Whatever you can roll as a group for them you do, saves time for you and leaves more time for player fun.