I use my own. I don't see the point of using someone else's TBH. It is such an integral part of the game - so if you are using someone else's tactics are you really playing the game? Or just selecting players?
I agree with GC. Ideally, you want to make a tactic that fits your teams strength's and your players strength's best. If you make your own tactic, you have an understanding of what you are trying to achieve within your formation and what to change in certain situations. You don't get that with someone elses tactic.