It makes sense to work as it is, aside form maybe the fact that it can apply to other characters than one with no penalty. It working on one character with NPC party members makes sense, and is in no way broken.
I personally LIKE the fact that it works as it does, in fact, allowing you to really have a 'main character' feel while still having minions.
It works for every char the same, it does not matter if you give it to your main char or your minions. You can give it to everyone.
If you have a team of 4 people with +70% Vitality and +2 AP per round, I'm pretty sure the rest of the game will be far to easy. You can probably kill enemies who are several levels above you with ease.
I wonder if it matters, if the second main char was created by a player, or if somebody different really needs to controll it.
