So, here is your bottom line.
Let's see if that squishy rogue has addressed it already.
Oops, yep, all over the thread there's that bit about threat reduction.
If the rogue doesn't pull aggro then he doesn't need to worry about going splat. We already have posts in this thread by people who play rogues stating they tank Horoth. So your one example represents a miniscule part of the game -- not even close to "lots of things."
The fact that you repeatedly resort to name calling and insults shows the weakness of your position. If you had facts on your side you wouldn't need to resort to such immature behavior.
Survivability. How about evasion and improved evasion. How about -40% or more threat reduction so that the bad guy doesn't pay attention to you. How about diplomacy so that the target sees you as his friend and the other characters as the real threat? The rogue has an entire arsenal of options available.
In your lame example you never answer the question. Why would a rogue be tanking Horoth.
Oh, wait, yes you did. Its because the barbarian who is suppose to be tanking can't keep the hate because his DPS is so low (because he's undergeared and doing elite Horoth with the rogue who is fully tricked out). I remember it now. Lame on top of lame.
Send it the big, dumb 800+ HP barbarian who cannot hold hate to tank. That's your plan? Hey, I'm not as stupid as you seem to think. If that's your plan then the rogue backs off his tricked out gear so he stays below your 400 HP worth of damage.
But, we are talking best DPS builds here. And it is clear that, in spite of your immature and lame perspective that you cannot discount the rogue as the top DPS build in most content.
If my (or any) rogue is stuck tanking Horoth elite it is because your barbarian sucks. That, young man, is the whole story.