Failed design? Your tent may have been a failed application of this design but the two pole wedge design is a solid design that has been applied successfully in many, many tents.
Some outstanding applications of the design include tents by Black Diamond (Bibler), Integral Designs, Rab, Big Sky, Marmot, and yes, Nemo.
In fact, I survived the worst storm of my life in a wedge tent- the Nemo Tenshi. In winds estimated to be over 70mph, the Nemo tent was a survivor. http://www.backpackinglight.com/cgi-bin/backpackinglight/nemo_tenshi_tent_review.html
Every design has strengths and weaknesses, but the wedge design is far from a "failed design".