Right I meant appropriate. Your last example is one that the DMG describes so: "Encounters with more than a dozen creatures are difficult to judge. If you need thirteen or more creatures to provide enough XP for a standard encounter, then those individual monsters are probably so weak that they don´t make for a good encounter. That´s why Table 3-1 doesn´t have an entry larger than twelve for "Number of Creatures"." To make it a better encounter for a CR 10 I would not use 16 2HD Orcs but 12 CR 3 enemies.