Cake too sweet AND fell apart

I delivered a beautiful two tier (6 in and 10 in) cake inspired by Finding Nemo this morning (I'm about to post a picture so go check it out). My customer just emailed me saying that everyone loved the look of the cake but: "it was way to sweet, there was so much frosting in the middle it overpowered the taste of the cake and the pieces just fell apart. So a lot of people didn't eat it, and that was a bummer. But it did look awesome."

I know I can't be everything to everyone but I really want to learn from this. It was a chocolate cake with peanut butter frosting for the filling (same cake and frosting I use for my Chocolate Peanut Butter Truffle Cupcakes, which my customer tasted). The cake was going to be outside in about 90 degree heat so I used my butter/shortening recipe for the frosting (which my customer also tasted and even preferred over my all butter vanilla buttercream, which she thought was too sweet).

I baked two 10X2 and two 6X2 and torted and filled them, giving me four layers of cake and three layers of frosting. I put four bubble tea straws in the bottom (10 in) tier and one long wooden dowel through both tiers.

What I think happened: the cake:filling ratio was too high for this customer. I typically have four layers of cake and three layers of frosting because I like the height and look of the cake. Until now, I haven't received any complaints about it. Do you think I should offer my cakes in two ways: the current way and one with more cake?

Any feedback would be great. I'm really bummed about disappointing her. But hey, on the bright side: everyone loved the look of the cake, including the birthday girl!

Yea I think it was a combination of how I layer it and just puttin too much. I did my icing dam differently that I have in the past and I think I made it taller than usual and this put more pb frosting.

Do y'all had a standard amount you put in? Do you measure it each time of just eyeball it?

Thank you Barbara Jean!! That was very kind of you to say.