I haven't found that beef in the mix is beneficial. I think straight lamb works better. I'm working on one for the rotis that's similar to the one posted above--a few more spices in mine. I'll post it when I can get it the way I want it and you can see if it works for you should you decide to try again.
Good tzatziki--to me--requires draining the yogurt (check the label, you don't want pectin or tapioca in it) and using plenty salted, drained, and squeezed grated cuke along with the onion, garlic, evoo, and mint.