With the advent of the Holy Shield buff, there's simply no such thing as too much mastery -- except, you know, past the hard cap for raid bosses. That's too much. But! Up to that point, you should approach mastery the same way a grizzly bear approaches a tumultuous beehive: You want to inhale as much of that sweet, sticky mastery as you can before you get stung to death by the swarm.
I've talked about combat table coverage before in one of my first columns, and while not much has changed since then, the advent of a new tier has made complete CTC all the more attainable, and the introduction of the new Holy Shield has made it all the more desirable. The more normal hits you are able to take to the face, the less potent your Holy Shield is going to be.
We want to mitigate (har, har) that downside to the cooldown, and to do so, we need to stack as much mastery as we (safely) can. I add the word "safely" -- scare quotes and all -- because safety is key. If the mastery is the delicious treat, the ornery bees are the constant threat of scooping up too much mastery in your greedy paws and suffering from a survivability loss as a result. There's always a break point between just enough mastery and having so much that you're trading off too much stamina and avoidance for it. In the end, you'll have to feel that out for your own purposes.
That said, in this column, I'm going to outline four easy ways to boost your combat table coverage -- by hook or by crook -- so you can scrape your way to the magical 102.4% number. I'll go over an amazing addon that'll visualize the process for you, a spreadsheet that can remove the fog of war from the whole process and make gear choices much more transparent, proper consumable choices you can make, and more.