I really don't know much about Yorkies, this is my first and I know even less about coats BUT . . . We had 6 month old Nikko shaved about a month ago and I think he turned out pretty cute (I might be biased though
hehe). His coat was very matted and no matter how much I tried to comb/brush it out, used detanglers, it just wasn't working. I took him to a highly recommended groomer and ask them not to shave him unless they had to . . . Of course they had to! I was upset at first but when I picked up him an hour later he looked adorable and they said he did pretty well with it, considering it was his first trip to the groomer. No mats to date (it's been a month).
Here's a before and after . . .