Scholomance could be pretty hairy too. As for tanks ... honestly in my experience tanks were more valued for their dependability than their "skill". They had no rotation as such, spamming sunder gave insane threat, shield block and mortal strike on cooldown and spam heroic strike. No decent tank took more than 15 points in the prot tree anyway (just enough to get Defiance), the rest was spent in Arms for Mortal Strike (few points in Fury for Cruelty)
Scholomance was a waste of time. Sunken Temple too. Not a single worthwhile item to get.
Threat was an issue if you played in a high tier guild where everybody wanted to top the DPS charts. A few bosses had aggro resets. Most guilds had a rule of thumb "start DPS on 3 sunders", but when you had 3 rogues with TF in the raid, they would have to wait a little longer.
I never said anything about having to put a lot of points into the prot tree. Talents were irrelevant back then because everybody had the same builds.
Stance Dancing on a boss? Suicide because you lost your damage reduction and you typically weren't crit immune unless you had full tier 2 with Styleen's Scarab. Tanks had to up their game in AQ and Naxx, but then so did everyone.
You had to stance dance on Magmadar, Nefarian, and IIRC if you were good you could also time it on Onyxia, unless you played undead (which I did) or Alliance (in which case you're a big faggot and had easy-mode throughout Vanilla anyway).
Okay, maybe not HAD to, but if you were quick and good it was a good thing for the raid. As long as you told healers.