Secondary skills in Heroes 3.

Hey guys, explain to this clueless elf why diplomacy is so great. Usually, you end up recruiting useless weaklings. You already have a sufficient army, and it feels like a waste to use a skill slot for it. There are too many "ifs" in this diplomacy, in my opinion; like "if" you're playing as Barbarians and "if" it's the month of Ruukh and "if" Ruukh creatures are in the way of your hero and "if" there's a slot in the army for them or if there's a unit you don't mind disbanding and "if" they encounter your hero along the way, and not clustered at the opposite end of the map, and "if" you have a large enough army so they don't scatter... then, yes. But there are too many "ifs"...