For the normal flow in this industry in terms of doing trade in the exchanges site when bitcoin rising up the value it is normaly altcoin will goes down. If you think altcoin is helpful to you, then why not, I don't see any wrong if we buy altcoin if their price value is crashing down especilally if all the top 10 listed in the coinmarket.cap is being reduce. Then if bitcoin down again its altcoin turn to goes up just simple as that to understand.