It's a paradox, humans are perfect in their imperfections. Life is growth, like music is multiple notes, it's beauty is in the change but we are always trying to hold on to this idea of a constant. To assume humans are a failure or a design flaw is to assume what we are judging is a complete picture. Our perspective and our assessment of how it makes us feel is all this question really asks, and the answers to those questions are very limited by our own ignorance.

You are alive, its not a failure. Perfect is a feeling we came up with, life is perfect, it's just not perfect to us.
"Normalcy is an illusion, what is normal to the spider is chaos to the fly."
Do you feel the divine nature of the universe when you see a spider making its web, or catching its meal?
The spider and the fly are perfect, people just like to argue about the nature of things when it effects them negatively.

I think this question highlights the imperfection in humanity as well as any answers in responses could.

It's a modest and possibly innocent attempt. It's kinda cute though.

The question is based on an unsupported assumption, I don't agree that humans are a failure.
Against what criteria... can you describe a perfect being?
From a Christian perspective, as I understand it anyway; the whole point of this life is to establish an eternal, mutual relationship with God. Or... not.
Any relationship must be voluntary to be mutual. To hard-code a bunch of minions with a desire to hang out with you "designed-in", would ruin the whole point. They need the free will to either accept or reject the offer; to choose an option.
Options imply incompleteness; on-going development.
The notion of perfection implies completeness. Any variation on a perfect subject would necessarily be an imperfection. That leaves no room for growth or free will at all.
Ironically, that doesn't sound very perfect.

To ask whether human imperfection is the result of design or evolution, is really just to ask whether you believe in intelligent design... or evolution; which is another fallacy.
The two are not mutually exclusive. Evolution is a theoretical process, a mechanism. The theory itself does nothing to address the question of how that process was initiated.

It is just simply a way to ask whether a God could be the source of humanity, because he created an imperfect being. It to me, fails to rationally consider that if a perfect being created beings who were imperfect, there may be reasons we imperfect beings can't understand. A perfect being may create imperfections to achieve goals we have difficulty understanding.

First the question is based on an assumption that does not necessarily have to be true, is not a fact, but a personal opinion of the person who posed the question. Why does it have to be a failure of any kind? We are spiritual creatures, made by a loving God. If anything "failures" come from not knowing and/or understanding God's will in our lives.