Need faster reheating of frozen vacuum packed roast beef
That would almost certainly overcook the outside while leaving the inside still frozen, depending on how the package is shaped and the meat was originally cooked.  

It takes time for the heat to penetrate the meat, which is why sous vide is classified as a "low and slow" method of cooking.  Because your package is frozen, in order to bring the meat up to temp it has to thaw first, which takes even more time.  Depending how thick the package is, if you pull it out in 15 minutes it is entirely possible that the inside will still be frozen.

If you cooked the meat sous vide in the first place, an merely wish to use 200 degree water to reheat it, you will over-cook at least the outside of the package, again depending on the size/thickness.  If you cooked it in a more conventional way, its still possible that you will overcook it by using such a high temperature, as even chicken (which is usually cooked very well done) is only cooked to an internal temp of 165F.

Regardless, I would definitely expect some loss of quality if you reheat by boiling.  In order to preserve the quality (tenderness, juiciness, flavor), your best bet is to reheat gently.  Water temperature of 140F is generally recommended for reheating via sous vide.  It will however still take time.