A Wall Street strategist says the Nasdaq is 'extremely overvalued' after hitting a fresh-record high, and says that's 'not a healthy situation'

· *The Nasdaq's record high is "not a healthy situation" as investors are piling into one sector of the market that is "extremely overvalued," a Wall Street strategist told CNBC in a Tuesday interview.*
· *A small group of dominant tech stocks are the only ones able to survive in this environment of extreme valuations, Tim...