Alts are dependent on Btc movement any way Btc goes affects them. If an alt dumps, you look for a good entry and refill your bags provided such alt has potentials of bouncing back from the dip.
I agree even how stable is an altcoin once bitcoin dump or pump majority of alts are going same direction it only shows how bitcoins dominate the crypto market. nevertheless there are few instances that alts move alone while BTc are consolidating this is a good advantage for alts cause it can goes up or down when bitcoin are stagnant or consolidating