I think the most enlightening aspect of Dev's was pointed by the horse's mouth- "Mein jabb plan karne jaata hoon toh sabb gadbad ho jaata hai".
Yes, it's a study in contrasts. Unlike the vile Shaurya, the epitome of manipulation and deceit, using even his family as instruments, Dev is a family-oriented man who has a clean heart and is just incapable of manipulation.
He has made up his mind about seeking out the perpetrators of the crime, but good intentions aren't enough.
He doesn't possess far-sightedness, an ability to clearly discern uncomfortable home truths, and is not able to resolve his emotional conflicts well.
I'd like to suggest a parallel with a Shakespearean play that deals with revenge- Hamlet.
Much like Hamlet, Dev is delaying his course of action unnecessarily. And I think it has already cost him dear,considering that he got shot today.