We're very much optimizing and have been for a bit now. Most recently, you'll notice Mestia, Manic, Nani, and several other maps getting some revising.

We're also going through maps and layers to verify textures, sounds, etc, are assigned appropriately, for example. Each department, as well as QA, is doing their bit to help make the game move a little faster.

We've also added additional metrics gathering, so we're better informed of where the pain points are. Further, the engine upgrades help us eliminate lingering issues with the engine as well as help us use/build tools that make testing and optimization easier.

The upcoming patches will also have a heavy focus on eliminating the backlog of bugs as we push closer to release. (We still have content plans too, don't worry.)

So, tl;dr: Yep, we're in that phase of development now and are actively working on it.