You mention the success rate of Rescue being small. Well, I feel inclined to argue the the troll rate of Rescue users is more than likely to be just as small.

Either way, it doesn't matter. A troll is a troll. The fact that they decided to use Rescue in the middle of a fight and got you killed isn't worth fussing about.

That's like complaining about a tank using Limit Break in the middle of a fight that doesn't require using it. Or worse - a non-tank using Limit Break before an important Limit Break mechanic (Alexander). Does this mean we should get rid of Limit Break mechanics?

Also, a healer doesn't need Rescue to troll you. They can choose just to literally not heal you in the fight. You know, as "punishment". And then what? Are you going to cry about how healers should be removed from the game?

Basically, the point I'm trying to make is that the problem isn't with the Recue ability - it's with the player that decides to troll. And the way you deal with those players is by kicking them from your party.