Would this be considered secure?
As a previous commenter pointed out, you're describing the avalanche effect.  In a block cipher, every output bit should be dependent on every input bit.  Changing a single bit of the key or a block of plaintext should, on average, cause half of the bits in the ciphertext block to change.  

A cipher that exhibits the avalanche effect is not necessarily secure.  It can still have statistical biases or be vulnerable to attacks such as differential or linear cryptanalysis.