The only time this is good is when you have a high attack minion while your opponent have a lot of low attack minion. I think it's too situational for a 6 mana card. If your opponent have a 7+ attack minion, you can combo this with Big Game Hunter for a guaranteed board wipe but that's worse than Equality plus Wild Pyromancer / Consecration. It's not a bad card in other class but Paladin just have better options.
Bit overpriced I think, 6 mana for a semi-parallel effect is a bit much, I'd say 5 mana is better, but really hard to evaluate
The point is that unlike Brawl you are guaranteed to keep one of your minions, probably (in CP) your only minion. You still have enough mana left over to probably deal with whatever they have left, and if you're against aggro (most likely use for the card, like Brawl) then you may not even need to.
It's really a very very good card tbh. Keeping your minion is surely worth 1 mana.