The last beta version reduced some unnecessary overhead from looking up key binds. I don't think that was the main issue, but that's fixed at least if it was.
Now in terms of FPS itself, I've noticed the in game display can't be accurate. I used FRAPS and DxTory to checks FPS while the bot is running, and the FPS they show looks more accurate. So if you're judging performance based on the in game FPS counter alone, please get an external program and see for yourself if it looks right or not.
By limiting FPS, the in game display seems more accurate. I tested Dried Lake a lot with 10 FPS and the bot was working exactly as expected (if you're limiting FPS to 20 or below, you should use LowFpsHelper to fix delays caused by lengthly delays between frames. Make sure to turn it off if you're no longer limiting frames!) Now, can everyone actually bot at 10 FPS in Merciless with anything less than godly gear? Probably not, but the point is the bot is working exactly as it should be at a place where it used to have a lot more issues before the EB update itself. I do recommend 20 FPS at minimal, as low FPS setups are not supported by us, but in terms of if the bot had some serious issue that was making it unusable, I'm not seeing it still.
One thing to keep in mind, is the PoE client itself has changed a lot since pre-2.0. There's even more data crammed into it now, which happens each expansion and people have to continuously upgrade VM specs and resources to keep up. I do think the client has gotten a lot of performance optimizations, but there are still issues posted by people (most likely not botting with EB) in the main forums about stutter, latency, and other issues when using lockstep. These are things we always have to coexist with and work around the best we can.
For now, I'll keep my eye out on other improvements that can be made, but I don't think there's too much more to change (aside from OldRoutine/OldGrindbot, which have planned changes) to try and make it work better. We'll see how things go once some more new stuff is in place though.