Patch 3.1.3 comes mostly as one of those dreaded patches where we get or marginally useful abilities nerfed into oblivion because of those pesky arena players. Paladin pvp nerf, warlock nerf, business as usual. But there are two changes in particular that affect me.
First off, MIMIRON NERF! WOOHOO! There are now several changes to the Mimiron encounter that will make me hate it less. First, rockets will now prefer ranged. Not a big deal, as I've gotten very adept at dodging them now that the rune adds a giant pillar of light. Second, mine damage has be reduced, and they've been given an arming timer. Sweet, no more listening to my DPSers yell about having a mine get launched from the evil gnome and whack them in the head. Lastly, the Flame Leviathan Mk. II will become stunned when the middle section is channelling the P3Wx2 Laser Barrage. Thank you Blizzard, no more jousting with that evil things tiny, tiny hit box while trying to get away from the beams of death. I don't know which drunken developer came up with the idea of having the turret have a bigger hit box than the tank, but when combined with the wonky pathing AI introduced for Wrath, you've gained the ire of many a tank. Now Mimiron will be less of a random luck fest.
The second is a heavy nerf to Death Knight tanks. The armor bonus for frost presence has been reduced from 80% to 60%, bringing DK tanks back to their original baseline mitigation levels of 3.0.2. This is significant because it represents a step by Blizzard away from the homogenising of the tanking classes. Frost Presence was buffed up to 80% because in the initial days of Wrath, few Death Knight tanks actually understood how to play their class, they saw all these awesome cooldowns and used them like old school tanks used their trinkets, stacked. They'd pop all their cooldowns at once, and be invincible for a short while, then when they wore off, they were only slightly more resilient than your average Retribution Paladin. Having frost presence at 80% allowed DKs to have more armor and health than a Warrior or Paladin, and much better avoidance than a Druid. Then came the amazing cooldowns. The idea behind the DK tank is one of active mitigation. It's akin to the protection paladin having to spam Holy Shield on cooldown to remain uncrushable. A death knight must stagger his cooldowns, and pick and choose carefully where the most damage will be coming from, and when. This is why they get so many cooldowns, and on such a short turnover. DK tanking will now require more skill to maintain it's level of effectiveness, and should provide a decent challenge for players.