You should finish working on the heroes that you have already ascended to the final stage as you have already spend mats on them.
As for the plan for future development, there is no straightforward answer. It depends what your goals are. So I will answer from the standpoint of our alliance.
We prioritize Titan battles above everything else. So, we would recommend working on Wu Kong and Gormek as they are essential to increasing your titan scores after that Boldtusk.
If nothing changes in your roster when you finish those, then you can move on to 5* heroes.
BTW: our alliance is called The Headless Horsemen. We have an opening, and by the looks of it, you could use a change in environment. Check us out and see for yourself: Closed for 20 character