Let me qualify this statement first. In Dungeons & Dragons the race , class or a combination of both would determine the difficulty of the adversary. You would never find, for instance, level 1 players fighting Liches, Drow, Mindflayers and other powerful creatures. This is simply because these creatures are fierce adversaries and only experienced adventurers can take them down.
Vanilla WoW used to have a sense of that, I think. Abominations were powerful units in WC3, and the first two aboms that Alliance players encountered in classic WoW were elites, one in Duskwood and one in Andorhal. Attempting to solo them was suicide - attempting to take them down with a group that wasn't appropriate level was also difficult.
Skip ahead to Cata and we see that Blizzard have creatures with a huge range in levels. Trolls encounter a Naga Sea Witch at level 5ish, Forsaken kill many Alliance 7th Legion troopers (the elite of the Alliance army) etc.
Now, maybe I'm too old school, but I would think that a certain type of creature, for example Doom Guards, should never appear at low levels. I remember playing Baldur's Gate 2 that seeing a Beholder or Mindflayer was a crap-your-pants experience - just looking at the model you knew you're in for a rough ride.
I know that they are completely different types of game, and that Blizz do it for variety and excitement at low levels, but I was just wondering if anyone shared my views that certain monsters should have levels indicative of their power in lore.