Doing some quick tests with Empowered Seals post-SoT-nerf.
https://www.dropbox.com/s/62d8am975wbma ... .html?dl=0
In this sim, I'm switching up with buffs we're maintaining. ES_SoR, ES_SoI, and ES_SoT just sit in their respective seals with no twisting. ES_IR twists insight and righteousness, ES_IT insight and truth, ES_TR truth and righteousness.
ES_3seals twists all three (usual APL).
SoI is still the TMI winner, but IR is a close second. As such, there does not appear to be a survivability benefit to twisting all three seals.
SoR is the DPS winner, meaning there's little point in twisting all three seals for DPS.
The only niche the 3-seal actor appears to inhabit is that it's still a pretty good compromise between DPS and survival, but ES_IR isn't really that much less efficient. I suspect that in practice you're actually better off using SoI and SoR and just letting insight drop off while not tanking anything to boost DPS.
TLDR: I think 3-seal twisting is gone.