The drop in TRP is because of different reasons. Some being Balli's entry, too much Shaleen and many SidSa fans stop watching, because their story stop processing. The makers need to understand that there are two huge and different fanbase watching the show. One is very active on twitter and the others in groups, discussing and analyzing. One trend and the other make beautiful tread.
They can't have focus on two characters and keep the other fanbase on hold for weeks with less than 5 minutes screen time. MoRan fans are young people and they are mostly watching on free app. SidSa fans are working people and plus 18-20 and they watch on Tv or Sonyliv. Reason that the show was on the list on online TRP doing SidSa track. MoRan fans give popularity with their trending. So they need to keep both fanbase happy.
Balli was the mistake by the makers because Shaleen (sorry Shaleen fans) didn't manage to bring out the different layers the character had. His Punjabi was awesome and the look of his entry cool. But that's all. Many times doing Balli he slip into Karan and still do. To be honest beside his Punjabi and 2-3 different expressions you can't really feel the different between the two characters.
His creepy smile made him even more NOT likable, on top of that he molest Monami. But the makers are trying hard to change that and make the character likable. They are defiantly going to try with MoLi. Observing the young fans, the may even accept it. I mean, they did trend MoLi after the bar hug.
I don't think killing Karan was a mistake, because there was a need to do something big, to turn the story in a totally new direction and personally I feel the story has become interesting. Param is interesting.
They are trying to bring the story back on track. Karan may come back, but they better not show that Balli is Karan because that would totally destroy Monami's character and the tribute the channel gave Karan. Talli or Param saving Karan is the only thing that make sense in case they bring him back.
It time fans accept that the 4 leads are equal important and so are both MoRan (MoLi) and SidSa. Both stories need to be explored side by side.
About the story then Karan who played an important role in everyone's life dies will change all the characters, which is interesting and needed. Param with the terrorist's by choice or not - is interesting. Charu revenge and hate for Karan is interesting and Talli's character too.
Saying that Karan's dead is the reason of low TRP is not true because the drop happened already with Balli's entry and Aditya mentioned that in his interviews.
This just my opinion and observation.