Hmm, a one-player wrath, but it costs quite a bit more and a bunch of life - or in its second mode, it deals a bunch of damage (and just kills a token swarm player outright)

Interesting. Certainly needs to be rarer than this.

I thought it was the players in question who choose how many creatures to sacrifice. I guess the wording wants clarifying.

Yeah, the wording is hard to make but it's basically this:

You know about a plague, and you give the players you like the information to dodge that plague. The plague then comes and hurts the players.

It's a bit biblical.

Suggested wording:
"Choose any number of target players. [Each player chosen this way/Each of those players] may sacrifice any number of creatures of his or her choice.
Each player loses 2 life for each creature he or she controls."

Noted.