My syntax wasn't proper earlier. It'd be more like:
Conditional Branch: Script: $game_actors[<actor_id>].class_id == <class_id>
So, [Conditional Branch: Script: $game_actors[001].class_id == 001]
would check that the 1st hero is of the first class in the database.
So, if standard, it would check if Arshes is a fighter.
But, in thinking about it, it probably will not work the way you want it to since it would work for any character as long as that one character was the right class. I guess you might have to define a variable or something which determines who is using the item. I'm not a very competent scripter unfortunately, and I'm not sure what the syntax is to determine who is using the item in battle. I'll see if I can find it. In the meantime, maybe someone else knows.