It's completely common is bitcoin trading history because all other altcoins have completely depend on bitcoin so they need to take break until when the price of bitcoin will settle at one point.But really it will effect all other altcoin investors also due to rise in bitcoin price.
I do not see any vast difference in the price and the price parity wont affect the rest of the coins ,bitcoin is gaining momentum and so does many other coins but the alt coins btc prices has being a difference but the over all status is not that bad as some things it is.Yesterday Monero had a decent rise and so does Iconomi and several other coins .It trading and you are bound to see those rise and falls.
Yes you right any thing can happen in trading market, without ups and down how can a trading assets will work. The only thing every one should do when ever the bitcoin price increasing people should remember one thing that is you have to buy altcoin because we can able buy more altcoin so once bitcoin price consistent than you sell them for btc.