Each troop has a use, but..
Wardogs are better than Axes due to their greater mobility, and will chew up mages.
Bows are for peppering heavy melee.
The priest is the best troop by far either their range of 5, there is none better for a very long time.
The knights are amazing! They are a great, tough troop with a good initiative rating for the class. Their reach of 2 with the pikes makes them the 'go to' troop for many chapters.
Ahhh mortars. I love their great range, but they only move 1 and do not have a lot of health. A canny fighter uses Orc Strategists, especially when facing a lot of light melee. These are grown in a building, Grounds of the Orc Strategist, available for crafting in the Magic Academy.