But on a reply to the second half of your comment I'd say that Grasp is a very useful mastery against teams with little to no burst damage, the same with fervor of battle. For my experience the two masteries I use the most frequently are warlords and fervor. Grasp is an excellent mastery for trades but after the recent nerf, which is more than what people think it is, I feel like it's more optimal to learn how to play with fervor or warlords respectively.
I feel like Thunderlord's Decree shouldn't be used on Yasuo at all unless you're just looking to have a good time and just mess around a little bit. Fervor is probably the best mastery once you've actually learned how to correctly use it and abuse it In lane. It and warlords are undoubtedly the most gold efficient keystones. Even at level 2 which is where most match ups a yasuo would stop using either e and q as poke abilities and begin to try to all in, he'd gain a solid 20 on hit damage every swing.
Warlords is undoubtedly the best mastery against a team that has a lot of burst/AP, because it essentially allows you to build tanky after your two core items and take steraks gauge, sunfire cape, and frozen mallet into consideration.
Some items on Yasuo like Sunfire cape and Frozen Mallet are deceptively strong as a potential 3rd or 4th core item.