It seems pretty much confirmed we can see Ethereum going under $400 these days.
Qn - Is it a good buy under $400 or wait for even more price drop?
At the price of Ethereum, I now think it's a fitting price to buy some Ethereum then be on hold in the long run. Because I believe that by the end of 2018 the price of Ethereum will be very high compared to other Altcoin. You will regret if you do not have Ethereum.