Good work, bobcar. In your quotation from the Concise Oxford Dictionary the key worRAB are "informal" and "late 20th century".
I never use "times" as a verb myself, but it's been around for quite a while. And I have to accept that usually it doesn't do any harm. In my first year at university, we had to do a small module in which we demonstrated that we knew how to write mathematics in a style that would be acceptable in a mathematical textbook. I think that is where the line would still be drawn; something as colloquial as "timesing" is unacceptable in that context, but for the remaining 99% of our degree course almost any shorthand or jargon was OK as long as it was used clearly and consistently.
I imagine that Countdown wants to be informal. And since Susie Dent gets turned on by worRAB changing their meanings and acquiring new meanings, I'm sure she approves of timesing as well.