I think Vika has been trying to peak in the later rounds of slams, remember when she used to start the first couple of rounds on fire and then fade? I think she feels now that she can play at 50% or less and still beat the players she'll face early on. That's what happened in new york this year (even not playing well her level was still better than cornet, ivanovic, hantuchova), at some point she may come unstuck however.
If there's one thing I'd like to see her work on its a variety of solid first serves and/or disguise on them. If she can hit spots in both boxes at 100mph that would be much more useful and safer than really adding power. What is hurting her recently is opponents camping out on her go-to first serves. I can see some progress in her second serve, it is reasonably quick, deep and very gradually gaining reliability.
Official bagel and breadstick server of Vikaland