Can we make Katarina and talon viable tops?

To do that you would need to make them good against tanks. Making them good against tanks would break them completely. So no.

As AtheosisX has mentioned, these champions are not supposed to be effective against tanky targets. In order to be viable top, they will have to overcome barriers such as their weakness to any form of CC during their combo, and their lack of sustain and base mitigation.

But if they are to be made viable top while retaining their kits, they will surely be overpowered.