Me and my wife are planning to do a road trip from Prague to Dubrovnik in end of April to early May (3 weeks) and would like to know how feasible is this idea and what all things we need to consider while planning this trip to avoid last moment surprises. Any help is greatly appreciated.
​​​​​

You will likely face a very sizable drop off fee for renting a car in one country and leaving it off in another.

The area you are thinking of covering includes an incredible wealth of places to see and visit. I felt rushed with "just" 3 weeks in Croatia! IMO, you would do well to think about what you want to do in the time you have so that you can come up with a reasonable itinerary.

Good luck!

So what route are you currently considering? What cities will you stop at? Have you checked car rental prices?

Something like this

https://goo.gl/maps/S4q9Lkmkfmr

I'd say this is a decent suggestion!
What does the OP think?

Yup, the route suggested is nothing short of beautiful scenery. I love such trips when you pass by mountains one day and then walk on sandy coasts the next!