"Comparing the Legion which we were shown, several times just how powerful and terrifying it is" Not 100% true. Outside of the Broken Shore, and the 7.3 events, most of what was shown of the Legion is based off the aftermath of what happened, as the events that were being told of their power (Such as the Titan Pantheons demise, the infinite timeline controlling shit, the WoTA, etc) is practically expressed in books. Sure, we saw glimpses of the past, such as some WoTA stuff, and we do have the Argus and Sargeras feats in the Antorus Raid, but that's about it. The Sunwell was kinda weak (It's just the Legion taking hold of the Blood Elves' source of power to summon KJ, which isn't impressive), WC3 had Archimonde and the Scourge plot (Which the scourge stuff was a plot of the Jailer, not the Legion, as we figure out in SL), and TBC also had Outland...which well...was an aftermath of what was told in Books + The RTS games, and most of that wasn't even the Legion's doing (Outside of the blood of Mannoroth + some other sideline shit).