No it would still be busted in VGC to have a 60% offensive boost. A 30% boost is pretty fair for VGC, especially if it can “work with” the revival move. Where if you revive a Pokemon and that Pokemon faints, it will get a double boost for a potential 70% boost.
What if the "slight boost" is metaphorical and its attack increases by 100% for each fainted member? You could think that's too much, but put things into perspective: that's the bonus it gets for having a partner die in battle. Looking at it that way, any kind of attack boost as trade for a friend's death is definitely an "slight boost"