Made cupcakes with dh butter mix, added pudding, extra egg and sour cream as I normally do. When I took them out of oven to cool, they sunk in the middle. Deep craters. They were completely done, not doughy either. Why? 
Here is a link to a cupcake blog that talks about sinking..
http://cupcakeblog.com/index.php/baking-basics-troubleshooting/
hope that helps
Another member made the DH butter cake mix with added pudding and egg and it also sank. 
Think the butter cake formula is more sensitive to changes like excess sugar (pudding mix) which can cause cakes to fall.
The WASC cake expanded flavors recipe might work for you:
http://tinyurl.com/2cu8s4
(The cupcakes will have a small mound.)
Cake troubleshooting chart:
http://tinyurl.com/2p5bdu
HTH
Only a suggestion, but just looking at your recipe. I would not add pudding and sour cream. Add either one or the other. However, if you just have to add both add one cup of flour as well. Your recipe sound delicious. Please let us know how it turns out. 
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