I broke down the major damage—> toughness tradeoffs you can make here.
Collectively it gets you nearly 90% extra mitigation, which is a ton, more than any set bonus, but costs you 8-9 GRs worth of damage, which is also a ton.
I am personally not fundamentally against this state of affairs, but be aware that this will probably produce some rather extreme distortions on the leaderboard. Low paragon players will suffer an additional -9 GR penalty on top of the -9-ish GR penalty they’ve already got vs some player with 10k paragon. So now we’re looking at nearly a 20 tier difference.