On March 12, David Kim held an open Q&A on Reddit for a few hours. He answered various questions regarding tournaments and balance, and it's definitely worth checking out.
Q: Are any "large scale" or "mechanic" redesigns being considering for Legacy of the Void? For example considering changing mechanics around high ground advantage, the soft 3 base income cap, warpgate, etc?
David Kim: We're currently working on all parts of the next expansion, but everything is a work in progress. If something is problematic, we would discuss it and try possible changes. But one of our core philosophies on SC2 design is if the change isn't completely amazing, we prefer not to do it.
So in this specific case, things like high ground advantage working the way it does currently vs. how it worked in BW vs. other advantages we can think of that are different, it's really hard to clearly say that one mechanic is better in all the cases. Overall, we are trying various changes in various areas, but it's really difficult to say for certain what will go through at the end of the day.
When you guys have good suggestions on specific problematic areas as well as possible solutions, we definitely discuss and/or try those things internally as we work on the next game to be able to know exactly why or why not we're deciding on a certain area. Eg. We've tried and still retry things like different suggestions for the Swarm Host, more harsh counters to Force Fields, or old units like Lurkers, and so on.
For the full Q&A, click here.
Reddit - StarCraft II: Heart of the Swarm Balance Reddit Q&A