Tanking.
So much so, that the history of wow is one long story of making tanking easier. All the hero classes were tanks. The role shifted to being able to sustain yourself instead of relying on heals.
Increasing threat modifiers begins in wotlk and it was necessary. Try running TBC heroics early on and keeping aggro on a big pack while seed of corruption goes pew pew. Seems like bad design to force tanks to gear for damage just to keep the mobs.
Healing you just spend a few hours installing healing addons then point and click