Many people don't know exactly how long it takes to cast Cursna. And with varying degrees of Fast Cast gear, you're going to see different cast times. Unless someone is showing a 1 for their Doom Countdown timer, I doubt that it'll stop people from trying to cast a Cursna. I can sort of see your point, but at the same time, it's important to focus on the tanks and such, and deal with the extra DD as you can. Cure them first, cursna them first, etc.