Ok Ok wait did you just say basically " I going to practice this power I don't have to use it in my army, But I won't feel good using it" lol Just kidding ya really see Smiley face :0)
I don't think it's like that. If a spell targets your unit you can use your bonuses. if tring to dispel one not targeted at your unit you get no bonues and just a straight 6+ to dispel
so 4+ at your unit 6+ everywhere else