Sorry, it's late and maybe I didn't write my response properly. I didn't mean to say "Blizzard designed Vanilla WoW with the idea that some classes would tank some would heal and some would CC" I meant that Blizzards strict adherence to any trinity of "Tank/Heal/DPS" (as mentioned by the original guy I quoted) must have come later whereas during vanilla it wouldn't have been so strict as it wouldn't have been as solid an idea yet, due to it formerly being a "Tank/Healer/Control" trinity. Which again, may be complete nonsense *anyway*
Did you play Everquest? (I obviously didn't or I'd be stronger in my conviction
)
As for what it would look like, I guess take some of the absurd control abilities that come into play in later expansions like Ring of Frost, or that Death knight one (that worked on Ragnaros when it first came out); or strong as fuck debuffs that minimise enemy effectiveness and give it to a class that does bugger all damage like Paladin. Or a talent tree for priests and other support classes instead of the heal/heal/damage :P Balance could be more about control; and Elemental for shaman, just spitballing.
So yeah, none of this was meant to be a "This is how it was, durr" if anything it was more to air the alternative idea of the Trinity as I had heard it originally was; and see if anyone else had heard that or agreed
And all that just because I personally don't see a reason that a "Control" class couldn't exist in an MMO. It may not be a hugely popular class to play, or be stacked in a "try hard" raid comp; but it could definitely have a place that wasn't too unbalanced. Make the control effects scale with a stat, so they get better with raid gear. I need to go to sleep but I'm sure given even a few more moments thought it wouldn't be too hard to find a place for it.