Are these returns are actually "worth it" in non-registered accounts?

I've invested in a number of different risk bands. Perhaps too many A's and B's now that I think about it. My average weighed yield is 13.5%. After the Lending Loop fee, that is down to 12%. If I recall, my marginal tax rate is around 40%, and since interest is fully taxed, my return is down to 7.2%. This in of itself is okay, but to be realistic I should factor in default risk of 2-4%. This puts my final returns somewhere around 3.2% to 5.2%. Pretty low at the end of the day. Thoughts?