What a load of nonsense. Sylvanas should've had the Alliance, the Horde and several neutral factions baying after her blood even before Cataclysm.
You don't get much more plot armour than, "We have to stop Garrosh because he's gone too far! Oh hey Sylvanas glad you could make it back from your concentration camps."
What plot armour of Jaina's are people crying about? Because she survived her boss fight? Seems to me like whenever people cry about plot armour on Alliance characters it can be summarised as, "this character did something against the Horde but they're not dead yet? PLOT ARMOUR! BAD WRITING! LE GOLDEN DID THIS!"