To continue the discussion around exciting enemies in tactical RPGs (or any RPGs) it seems important to, at times, challenge the characters with families or societies of enemies. Rarely do civilized or sentient creatures stand alone in the world, without assistance, friends, or a community.
Such a family of enemies have the advantage of providing a set of monsters that have different strengths, abilities, and weaknesses, but are obviously interconnected. They often fight together, in different configurations, leading to different sets of challenges or changes in game tactics.
In addition to creating a exciting set of tactical battles, such communities of monsters assert the reality of these creatures within the world. Otherwise, the character might be scratching their head wondering why every ogre fights with a giant club... don't they have war leaders, shamans, scouts, hunters, and the like? My society does--what wrong with these creatures? Without the lack of an enemy community behind a sentient creature (or some other good explanation, such as a solitary spirit or mythical beast that spurns contact with its own kind), you may not come away from the fight as immersed in the fantasy world as you went in.
[The following collage contains some of the images of a enemy community with the Clouded Range mountains in Secrets of Steel. As a scourge of the isolated mountain passes, ogres will appear in 5-6 varieties and wield a variety of special abilities and magic--from shamans to bearshirts, to some ogres who have mastered and command a native and deadly mountain beast, the shiggroth hounds. As with other collages, I will post more progress here to the blog! I find this sharing activity very motivating!]