In my personal opinion, all crypto currency are directly or indirectly dependable on Bitcoin. When bitcoin gets down, most of the crypto currency also get down. Majority coins are influenced by the price of Bitcoin. So i think most of the time, all coins move together.
I agree with you about bitcoin dependency of altcoins. They generally don't move alone, they're linked to each other and the general trend of the crypto markets. This is how they move on the exchanges.