I would never recommend to anyone that they put all of their investment into just 1 coin, the risk associated with this is far too great. That isn't to see that it cannot be a strategy that works just that it is a single point of failure. I would pick 4 or 5 projects to invest with that way if one of them turns out to be a scam or fails for any other reason I still have the others to rely on in an attempt to cover and make a profit.
I don't see how diversification will be detrimental. We can select good coins out of many bad ones. I think diversification is the best strategy because it allwos you to still have profit even if other coins you're holding failed.