First- If CVs could come up with something extraordinary story wise and more importantly better actors were chosed for the role of Prerna and Anurag, may be then Komolika and Bajaj could have been avoided. As of now even characters like Mohini, Moloy and Nivedita (if we forget Komolika and Bajaj) look more powerful on screen as compared to the leads even though they share very less screen space then leads.
Second option would have been to get less experienced and lesser known actors for Komolika and Bajaj to avoid them overshadowing the leads. Whether wanted not these 2 characters have created a way too strong space for themselves even with less screen space, twisted story writing mostly because of how they portrayed their characters on screen.
Whether we accept of not both Erica and Parth have to learn a lot in terms of acting and they mostly survive based on the fan support (which is justified).