Horn of Gothos extends the range of the same zone Battle Orders, the built in small boost that the Orc Warlord can give.
This card, Sergeant Baras, extends an incantation command spell, like Battle Fury, and copies it to every friendly soldier. It cannot copy the Battle Orders skill in the way Horn of Gothos does because that skill is not an incantation. This means you can benefit from having both cards in play.
I think the ability is very powerful. With Ring of Command in play, a 1 cost Power Strike gives +2 Melee to many soldiers. It may be overpowered...