On the leaderboards, the top LoD Blood Nova builds use Nayr’s with Squirts whereas the top Trag’Oul’s Avatar builds use Trag’Oul’s Corroded Fang with Haunted Visions.
What is it about the LoD vs Set builds that lends itself towards these very different legendaries and play styles?
The Nayr’s setup is exploiting a bug where the physical damage of Blood Nova is being multiplied by the Nayr’s stacks.
The guy who got the first clear on the build said on his YouTube video of the clear that it’s a bug which in my opinion would make it an exploit… 
At risk of outing myself, I’ve played the build to see what it’s like and it is a lot stronger - but you need a very specific course of events, pylons, and anti-ToS third party tools [that I definitely did not and will never use!] in order to get their incredible times.
I know development of the game is dead so maybe this bug will remain in the game forever… so you’ll see this build whenever this season theme crops up if anyone’s still playing.
Why is it only used with LoD builds? Does the Nayr’s bug/exploit not exist when using the Trag’Oul’s Avatar set?
That’s a good question. And to be honest, I don’t exactly know. I understand that using it requires a bunch of poison skills in your bar which means it may hurt you and lose the 6p set bonus. And having Blood Nova in the bar means you can have a max of 3 poison skills so you aren’t maxing out Nayr’s (3/4). At that point Squirt’s + Nayr’s may not be as good as Haunted Visions + Simulacra + Trag’s scythe.
Hopefully someone with a more technical understanding will explain it better than me. Alternatively, look out for it on the leaderboards in the coming weeks. if someone can make it work, I’m sure it’ll turn up sooner rather than later.
Nayr + Squirt also need fast clearing speed to work at all. It uses the gloves bonus to protect the Squirt bonus, and if you don’t progress fast enough you will drop the squirts bonus easily.
I saw already a quite fast Inarius exploit clear listed somewhere. Traq set has lower dmg and maybe nobody bothered yet with it. There seems to be quite low interest to do any serious pushes with the lower performing sets.
Tragoul set bonus specifically boosts the damage only when equipped with “health spending” skills so Blood Nova Rune on your skills bar.
Just like Nayre with poison…
Those two setups dont mix appearently.
Nayre bug will be present in “4 cube slots” theme too.
Not gonna lie its pretty bad in this season, but it happens a lot in this game, we get bugged setups and they absolutely dominate the leaderboards for some time, both solo and team runs abuse Nayre bug a lot.
Kind of cool to notice 7 year old bug, the iron rose and nayre were added 7 years ago.
We have it bugged because back then there was absolutely no reason to test Nayre + Iron rose combo.
Its the first time it sees the light of the day i think.
We kinda can blame blizzard for not having even higher PTR exp rate, so nobody tested this because at lower paragons this builds isnt that great.
#edit
though it was reported 4 years ago… (now i know after checking)