I was sort of surprised that Skrillex didn't go lower than 40, and I was really shocked to see Peter Gabriel at 32!
Those old dubstep tracks really didn't go all that low. Now that Skrillex (and everyone else) has moved on from the genre, he's mixing in more and more sub 40 content. Check out his new collaboration with Diplo "Where are U Now" (doing nicely on the charts btw) which has some stuff in the mid 30s.
Speaking as a club DJ, what I've noticed is exactly what you did in those traces: Today's hip-hop is where the really low frequency content resides. That said, I'm good with subs that get to the low 30s - which just about gets it all if they can get there strongly. That 26ish note in "Nasty Freestyle" is kind of a quick thing that pops up infrequently amid a mind numbing low "D" drone (36hz).