Banisher Is a heavy missile tank. Its homing missiles have a pretty big range and deal massive (1000) area damage to both land and air targets, with a long reload time that leaves them open to counterattack.

A good hard-counter for the Hound, ideally when in groups thanks to it's larger Area of Effect. The homing missile cannot be dodged. It can also soften up units that may outrun your supporting army, like the fast Jaguars.

The Banisher also is a flexible AA unit: It kills most T2 threats like Roughnecks, Stiletto & Liche in 2-3 shots, though it's important to point out that:

The Banisher prioritizes targeting ground units first

Its slow turning speed can easily get it killed. When moving into fire, remember to keep its broadside facing the enemy so it can turn around and run. Use sparingly as a first strike unit for a devastating opening punch.

Never rely on Banishers alone, and always support them with other forces.