The weakest of all dedicated melee units, it should only be used in multiplayer/skirmish matches as better units are immediately available in the campaign. It's small tactical utility is in hitting exposed archery or low-tier polearm units.
Research in the campaign replaces/upgrades footmen with axemen, and later swordsmen.
Since their base defensive values are so low, Masterwork Armor stands out, being a flat bonus. Since using them correctly means attacking specific units and avoiding others, Ranger may help you outrun their frontline units and attack the vulnerable rear while the rest of your army ties up theirs.