The Uruk Hunters are fast runners and deadly skirmishers of Isengard. They tracked the Fellowship of the Ring, led by Lurtz. In 4.5, they received an overhaul which changed the way they function, giving them new abilities and new mechanics. They are now semi-heroic units, weak at the start but who gain twice the bonuses from leveling up; this means they can snowball very quickly.
Level 1: Hunting Arrows - The Hunters fire a barrage of arrows that deal heavy armor-piercing damage to enemy units and heroes, knocking them to the ground and slowing them by 50% for a brief duration. The hunters also move 50% faster during that duration.
Isengard Hunters are good early-to-mid game units. However, it is important to upgrade the Uruk Pit to level 2 relatively soon as enemies start attacking you with stronger units. Leveling up your Hunters allows them to continue to be useful in more of a support role, attacking a weakened enemy flank or harassing enemies busy fighting your stronger units.