Yes, that is the point. The group of the same type of enemies is usually deadlier due to knowing their own strength and can coordinate smoothly. It forces you to make a quick backup plan when too many enemies appear.
Just like a single wolf and a single lion, you can kill a wolf first easily, but if it's a wolf pack, then it's a whole different story.
Also with RC, you can gain a benefit when using the environment. For example, lure 3 of them to a narrow place which they have to go inside in a column one by one, this way they will lost the +3 bonus, and you can elimite them easier, (maybe I should mention this in the RC rule.)