Interesting.

Well, let's be very specifically on topic then.

Low level dungeons serve as training grounds; Losing threat here isn't deadly, but it is an indicator of improvement. Just about every dungeon pre-tank stance boils down into Throw-Aoe Twice - Threat Combo the focus target - AoE as needed to keep it off the healer.

Stone Vigil, when every tank is guaranteed to have their tank stance, is where losing threat is punished severely since things there hit much harder compared to previous dungeons, even Cutter's Cry. However, at that point, losing threat is completely on the tank, given the threat buffs that have rolled in nearly every single patch since 2.0.

You're making a mountain out of molehill is what it comes down to.