Blood Moon "smite" effect of buff seems oppressive

Was playing a game of blood moon, and partway through the game we had a small lead and had just killed 3 enemies (including any enemies that had stealth). We were taking down the herald, and then when it was around 10-15% health Diana appeared out of nowhere and killed it with an auto attack.

My immediate reaction was WTF? I realized that the "Demon Brand" buff grants your next attack 20% enemy MAX health bonus TRUE damage. That's insane. I get that it's supposed to be strong, but on the herald? Come on?

We just went 15-0 then had a 50 point swing against us because of the free steal. It feels like someone on your team needs to have the buff in order to do the herald, and it pretty much needs to be someone with a fast auto attack animation so that you can secure.

Fortunately we ( I ) learned from this midway through the game. When we were up 330-320 and a herald was alive our team called the herald and I said whoever gets it wins the game. We instead baited it like mad and got 4 kills from them running in solo to try to steal it. Nonetheless, I think it's pretty sad that the game came to this. There's no objective control in this game because the buff grants invisibility AND gives smite to anyone. That's a pretty lethal combination. For a 50-point swing in what has otherwise been consistently close games for me, I think it's pretty ridiculous that it's so easy to steal. Coordinated play has really little benefit.

I think the buff needs to be changed so it only affects champions (also prevents you accidentally blowing it on a spirit). Using it to smite the herald is pretty unfair. The Herald also seems to be worth too much, since there's really no way to secure it (no smite, all assassins so anyone can get in and go for the last hit) there should really be a tradeoff. As in it should be more optimal to take your chances 5v2 on the Herald than to just consistently try to bait the steal.