Except your wrong. Blizzards NEW Scaling Tech that was created specifically for Legion has changed things entirely. During the Invasions, on the Stage 4 Boss, Level 100's sitting in Mythic Tank Gear get rekt in 3-4 hits while low Level Twinks Tank them with no issues (no need to even BE a Tank). If you don't believe me go out and try it yourself.
All the Invasion NPC's scale to your Level BUT it's somehow favoring lower Levels far greater than it does Level Cap. These Bosses have a large variety of "Raid Mechanics" that have to be followed just like any other Raid Boss and when you don't pay attention to Telegraphs you die in a fire, literally. This thread, although likely sarcasm, is pointing out just how strong low Levels are with the new Scaling Tech versus how weak Level 100's are AGAINST THE SAME NPC.