Interesting to see this info!
Also interesting to note, the only non-legendaries that appear in the ~1000 level teams (barring the one goblin team) are:
Rock Worm
Deep Borer
Siren
Soothsayer
Valkyrie
Maralith
Mercy (though she might as well be legendary 
)
Half of which are mana creators (either transformers or spawners)
And some teams have as many as 4 unique legendaries. While in Cell’s ones all the teams seem to have at most 2 unique legendaries.
My theory behind all this is this:
Legendary troops are the best in the game (on average), so using them is a huge boost to your team (assuming done correctly). But as you said in the other thread Koolbiird:
So the lower levels are forced into a more varied meta because they have no other choice. They have at best a handful of legendaries, and likely won’t have them with more than 1 or 2 traits (if that). While at the top of the level curve the players have more resources, and have accumulated not only more cards, but also more traitstones, allowing them to trait their Legendaries (and Epics) up to 3 traits to get some of those VERY nice 3rd traits. And once you have those, the lower tier rarities generally can’t compare, so teams get built with mostly legendary troops just to be competitive. And since there is a smaller pool of competitive troops, the meta is a lot less varied and more stagnant.
So possible fixes would be either just more Legendary troops, or closing the power gap somehow between Legendary and the other rarities.
Just my thoughts.