So I bought a few individual characters to try out on the mobile version , but later realize they are also comes in a bundle with scenario and cards. Was it a waste of money to buy individual hero or will the bundle be discounted depending on what I already have.

So far there is not reduction in price if you own something From the Bundle beforehand.

So calculate what you have so far and compare it to the Bundle. How much would it cost to buy everything in Bundle compared to buying rest individually.