Initial Tanking Rating Thoughts

Today we're going to be attempting our first raid of the new expansion and as such this marks the first time I've really thought about tanking stats in a few months. I should head out and reforge my gear, but I don't know what to reforge to! I intend to really model this stuff out in the future and getting data from an initial raid will certainly help that, but for now I want to just do some napkin math and get something started. So I need to get a rough idea of what the different stats do. I did a look at some random World of Logs recap and found a boss swinging for about 20k. I'm going to assume he swings every 2 seconds. I also assume I hit Death Strike every 8 seconds and maintain debuffs with free runes from Runic Empowerment. I also seem to not have threat issues at all on anything I pump Rune Strikes into, and it can't be dodged or parried. So...

• Expertise Rating - absolute garbage
• Hit Rating - helps keep debuffs up in a timely manner, helps Rune Strike hit, still pretty bad
• Haste Rating - lets me Death Strike more often I guess. I will do more math on it for sure, but my gut instinct is it's garbage
• Parry Rating - 1% parry negates 100 damage every second in the long term. It takes 177 parry rating to get 1% parry, before diminishing returns
• Dodge Rating - 1% dodge negates 100 damage every second in the long term. It takes 177 dodge rating to get 1% dodge, before diminishing returns
• Mastery Rating - 1 mastery makes Death Strike put up an extra shield for 6.25% of the amount it healed for. With 140k max health it will heal for a minimum of 14k, so 1 mastery prevents 109 damage per second in the long term. It takes 179 mastery rating to get 1 mastery with no diminishing returns

If the boss hits harder or faster then parry/dodge get better. As I get more health or as I get more parry/dodge then mastery gets better. If the boss does a lot of non-avoidable attacks like magic then parry/dodge get worse. If the boss hits hard enough for Death Strike to heal for more than 10% max hp then mastery gets better.

All told it looks like mastery is probably the best and is what I'm going to reforge into for now. We'll see how things stand after tonight, though!