At the end of every expansion blizzard has created some kind of way to nerf the final raid of the expansion with buffs/debuffs/items in order to make the instance get progressively easier. Previous tiers usually don't get touched because the next tier nerfs it by offering better gear however the last tier doesn't have this option. This has been done many different ways and has been different every expansion. I am curious which one people prefer.
*Note*
Please don't post "I don't think they should nerf the final raid" just to sound cool, this topic isn't about if they should or shouldn't, this is about which of all the methods did you like the most (or disliked the least).
Vanilla - Pre Expansion Patch Nerf.
I don't fully recall this one as it was a long time ago and I was switching classes but I remember many classes being extremely overpowered and raid bosses which were hard were now a joke. The TBC patch changed many specs so they were useful and in tern made some classes/specs overpowered. Also difficult to get PVP gear with really high ilvl was made easy to get.
Burning Crusade - Flat Percentage Nerf
At the very end of the Burning Crusade blizzard was afraid with all the changes coming in the expansion that bosses would get harder so they nerfed literally everything by 20-35%
Wrath of the Lich King - Progressive Health/Damage/Healing buff
Sometime after the final raid was released a buff was activated increasing all health/damage/healing by 5% to everyone within the raid. This buff increased by 5% every month until it reached I think 35%ish
Cataclysm - Progressive Health/Damage nerf
Same thing as Wrath except this effected the raid and not the players, every mob in the raid had their health/damage reduced by 5% and this increased by 5% every 5-6 weeks until it reach 25%ish
Mists of Pandaria - ilvl Upgrading.
This was the first time blizzard didnt add something that they controlled, instead the players had to work at it to nerf the raid themselves. Every item that dropped could be upgraded 4 times increasing their ilvl 4/8/12/16. This worked similarly to the Wrath buff but it was only about a 8%ish buff to each player. Also players had to farm valor to upgrade their gear, the raid didnt nerf itself.
Warlords of Draenor - The Legendary Ring
Similar to panda but instead of every item being able to be upgraded you could u[grade your Legendary Ring. Killing Archimonde in Normal /Heroic /Mythic dropped an item that buffed your ring 3ilvl. This may not seem like a lot but it also increased the use effect by 1%~ and eventually it could reach 48% damage/healing + the after effect.
Personally I prefered the MoP or Cata model. I dont like the buff/debuff tied to 1 item and the requirement to kill a boss to upgrade it (and it doesn't even feel like your that much stronger), and I didn't like the high numbers from the Wrath model that made you feel weaker outside the instance.