I dont know what the format thing means, but the greater rifts are ridiculously hard right now. I can run anywhere around torment 10ish, but greater rifts? Im dying on torment ONE. I mean, a couple weeks ago i was doin em no issue, now its seriously an issue, im missing the 15 minute mark because its INSANELY DIFFICULT, even on torment ONE. Im almost paragon 300, i wipe the screen with ease in normal rifts at higher difficulties, and while i understand a greater rift should be harder, this is too much. Its not fun, its frustrating, i turn the difficulty down anymore and i might as well not even play!
I would very carefully check your items. My suspicion is that you switched out an item, leading to losing your 6 piece bonus. This could be due to inadvertently using a green of the wrong set or unequipping the ring of royal grandeur (either being worn or in Kanai’s cube).
Also, double check that you are using the correct supporting legendaries and/or legendary powers.
The GR difficulty is separated from your Torment level.
A GR 1 will be the same difficulty on Torment 1 and Torment 16.
When opening the GR you choose the level. Maybe you did choose the first option, which is always the hardest GR you have currently unlocked.
Every level increases Monster hp by roughly 17%.
So 5 levels difference already means Monsters have twice as much health.
With the second option you choose exactly the same difficulty as the previous rift.
And with the third option you can choose your level.
Your Torment difficulty does apply to Nephalem Rifts though.
As reference Torment 16 would be roughly equivalent to GR70