That item is bugged, if you get damaged by the boss it insta charges, any damage the soldier gets from bodss it instacharges the rage, very bad thing with bosses like rappy,a pipe can deal only 10 damage but the soldier can deploy the battalion and ruin the rage.

I agree.
The battalion backup is as effective as a ubercharge and can protect a lot of players but it is too easy to farm:
The max dmg a boss can deal with meelee is 213(heavy sauce's fists) not counting slenderman that deals 600+
A battalion backup soldier has 230 hp.
If a boss hits a BB soldier he will have only 35/27 hp so he can survive and be able to activate the buff.
Some boss weapon like the charizard and nyancat flamethrower,rappy's grenade launcheretc
Deal low dmg (usually from 8 to 15) and high firing speed
So the soldier can just get hit once and be immune.
My idea is to totally remove the ability of the battalion backup to get fully charged if hitted by the boss

The reason why the rage fills upon any sort of damage from the hale is because before the Battalion's Backup received a buff back in the summer of 2013, it only used to gain rage when you got hit for 600 damage, not when dealing damage. So it was only natural to change it in ff2 so that it takes only one hit in order to activate it. This is also the reason why it adds 10 extra health. But Valve decided to buff it and it hasn't been changed in FF2 ever since.