We are putting this ally to great use in our 4 mono-sphere Fellowship. It has good value for its cost, with a good attack value (that can even get up to 4 with Boromir's help) and a great Hit Points pool. Even if it's only confined to mono-Tactics decks its ability can be really useful as being able to engage enemies from the staging area (even if you would end up not killing or even damaging them) during the planning phase can be amazing. It can even kill some weak(ened) enemies on the spot, and you can do it for basically only 2 cost if you happen to have Mablung around. There are also other good timing combo I guess (like with Hirgon and Prince Imrahil after the Enemy attacks part of the combat phase).
Knight of Minas Tirith
If each of your heroes has a printed hero resource icon, Knight of Minas Tirith Tirith gains: "Response: After Knight of Minas Tirith enters play, choose an enemy in the staging area. Engage that enemy and exhaust Knight of Minas Tirith to declare it as attacker (and resolve its attack) against that enemy."
Assault on Osgiliath #84. Tactics.