ddaigle, if you used the original recipe, it is a sure failure in my opinion. I don't even know why they chose that recipe. It isn't balanced except for ideal conditions and then still not great.
Use my changes above, which really happen to be those of a phenomenal baker, LindaF144. I don't see her on CC very often anymore, but she did open a retail shop.
To clarify, 1 cup, or 8 oz sour cream instead of the milk. I also add about 3/4 tsp of espresso powder, but that is optional. If you do add it, drop it in the hot water. I do use hot tap, not boiling and it is fine. They just want the cocoa powder to melt into the ingredients. This way you don't get that powdery cocoa taste.
Have all ingredients at room temp, even the sour cream. Just pop it in the microwave for about 20 seconds. Eggs, run under hot water in a bowl. Sift ingredients. Add eggs, one at a time, fully incorporating each one before adding the next, maybe 15 seconds apart, on low. Once you add the rest of the ingredients, mix on med if a hand mixer, med low on a stand, ONLY until incorporated. You will be able to see the change, about 1 to 2 minutes.
I always use baking strips and a flower nail. Make sure your oven temp is correct.
Use the above method on most scratch cakes and you will have good results. Your box mixes will even benefit from room temp ingredients and slow egg additions. It helps make a homogenous batter.
If you really want to be OCD like me, use a chocolate thermometer and get your ingredients to 72 degrees. After awhile, it will be ingrained and you will just know room temp.
Another helpful scratch hint: Room temp butter is also 72 degrees. It is firm, but can be indented with your finger. If it is soft, it is usually not at the optimum temp for a cake recipe.
If you still have a problem, let me know. But this should come out perfectly for you. Susan