This is probably the best of the Dragons if you're ahead. Preventing them from playing combat tricks during combat is solid and is going to keep you ahead. White is accustomed to getting fliers, but it doesn't get a ton of dragons (Is this the first uncommon white dragon ever? Someone out there has to know). I like this card a lot. I imagine this will be a snap-include if you have white in your deck in Sealed. I can't say when it's ideal to pick this in Draft, but I'm likely happy with it.
The one thing that sucks about this in draft is that white has the best combat tricks, and you're likely taking a lot of them so you have to worry less about them anyway. Still, there is plenty you don't have to worry about, and forcing them to play removal pre-combat helps you make good decisions. This is a solid card.