Just because vanilla had a proper progression line doesnt mean its truely difficult

- however compared to todays encounters, sure, it was, you couldn't reach endgame content in a few weeks or skip entire dungeons, as the general consensus of Blizzard became that all content had to be available to even the worst players, which is a natural action as a business plan which doesn't support that idea isnt as efficient and profitable, theres a reason Naxxramas was copy pasted into WotLK, and the above mentioned consensus started shining through Blizzards content more and more. One instance was made, it could both be played by 10, 25, normal, heroic and additional achievements - 4 modes, 1 dungeon, - more content, less scripting.