I'm a bit confused as to why you say Vika had much more problems with Aga than Caro before 2012. As of the end of 2010 (Caro & Vika's last full match was in the fall of 2010), Vika's head to head was 2-4 against Caro and 4-2 against Aga. In 2011, Caro and Vika only played the 3-0 retirement set while Vika went 2-1 against Aga.
Fun fact...as far as I'm aware, Caro's highest winner total in one set is against Vika and her highest unforced error total in one set is also against Vika (two seperate matches).
I was more reflecting on a matchup changing in Vika's favour using the Radwanska example as a direct comparison (to keep it short and brief). Reading what I said I think you have misunderstood the context of "much more problems", I meant Vika had much more problems with Radwanska - the H2H was in her favour, but it tended to be tight, now most neutrals don't even want to see the match anymore. Not "much more problems" than with Caro which I think you have understood my post as, so sorry for that confusion.
On to the Caro matchup, 2-4 is negative but doesn't tend to necessarily suggest actual matchup problems (especially when one is a retirement after 3 games). It's not 0-5 or complete beatdowns. Take the last 2 completed matches, Caro won these because she was the better match player. Now I know you are big Wozniacki fan (I like Wozniacki too fwiw), do you really think this is the case anymore? Caroline at the time of the Tokyo match was one of the mentally toughest players on tour. You believed the majority of times a match got close she would tough it out. She did this endlessly in 2010, toughing out matches. This just isn't the case anymore. She is actually mentally weak in tight moments now. A lot of Caro's 'decline' has been mental imo, your game declines if you lose belief and confidence.
The technical side has also changed. Vika has made great strides in most of her game since 2010, she has improved in nearly all aspects. The same isn't true for Caro, Caro for whatever reasons hasn't really technically improved her game since 2010. As a result, your game then declines if you suffer a big loss in confidence.
If they were to meet tomorrow, it is hard to predict anything but a Vika win imo.