I doubt they would go for 2-3 minute recast but even being castable on others 10 minute recast is way too long, I fail to see how gamebreaking it is to half the recast since you would need perfect timing just to get it to be useful on others in the first place due to what you already said. Even if you give it to others it could be wasted if the situation changes. I don't think Plds and Nins would complain much about having it used on them though.