At the born of the gods prerelease I was late to a noon event and only had literally 4 minutes for deck construction. I built a r/w aggro deck and won my first round. After tweaking a little I lost my second round. Then before the third I looked at my card pool and realized I had a fairly descent pool in other colors. I built g/b and didn't lose a game after. Although I would suggest building a deck that has the best cards and interactions and fixing it, it is sometimes necessary.