Banana Strawberry Cupcake - Just okay

I had some browning bananas and frozen strawberries, so guess what I did? The banana cupcake recipe was adapted from

http://www.vanillagarlic.com/2008/05/banana-strawberry-cupcakes-with-cream.html

I split the recipe by 3 and did some slight modification since I wanted more banana flavor, more strawberries and less dense cupcake. I also wanted to try adding strawberry yogurt in some of the cupcakes.

1 cup all purpose flour
1/3 cup sugar
1 teaspoon baking powder
1/8 teaspoon salt
=> Mix together in a bowl

1 egg
1/4 cup vegetable oil
2 bananas
1/2 cup chopped strawberries
Grated lemon zest
=> Mix together in another bowl

Add wet ingredients to dry ingredients. I divided the batter into 2 and made one batch without strawberry yogurt and another with 1 teaspoon strawberry yogurt per cupcake. Stir until just combined. Bake at 350F for 35 minutes.

The one with added strawberry yogurt did not rise at all. I am never using yogurt again in baking muffins and cupcakes.

The frosting was from

http://simplyrecipes.com/recipes/cream_cheese_frosting/

The frosting taste awesome with the cupcakes. But the cupcakes were still too dense for me and the center seemed a little uncooked even though the top was already quite brown. I am not sure if I put too many bananas since I put 3 times more than the recipe asked for. It taste quite nice just out of the oven but was really dense when I had them again after about 10 hours. This recipe is really good for making banana strawberry loaf (something similar to pound cake).

Note: Got some tip that oil causes cupcakes to be dense. I should try to eliminate oil altogether and see the difference.