My guild is still a bit behind because of a few last-minute issues with our roster (some members quit WoW in the last month, been a mess to replace them).
This first part of the first tier looks very challenging.
Some combination of Stone Guard dogs can be really hard to manage, second boss requires you to use the tricks of the crystals to make it viable, third is a time-race, fourth is very easy, Elegon feels hard and we haven't tried the last one yet.
On paper some heroics look really hard.
Despite all of that I'd say that T11 was harder, imho. Not much, but a bit harder for sure. Altough it's hard to make a 1:1 comparison since they still have to release more raids of this same tier, whereas T11 was released all at once.
So far I'm pretty satisfied by the fights, altough I still hate mechanics like StoneGuard/Halfus, where a boss changes radically from reset to reset.
Paragon said that perhaps the kill would have come a week earlier if attempts were unlimited, no more. Enrage was the problem, not mechanics. Fight was a very big gear check. Can't find the quote right now.
I'd say it's probably the same or this tier is harder.
It's just a completely different model to be honest. We had a week before raiding opened up, then another month for the next tier, and another two weeks for that tier. Sure the top guilds are going to gear fast, but this only raises the level of which you can be prepared for the content. Compared to MoP people doing T11 were way less geared and prepared, that's why things seem to be dying fast.
Also T11 content was extremely buggy and it took awhile for them to acknowledge/fix things. Say what you want about 10 man difficulty, but outside of 4-5 bosses, the rest were impossible with launch tuning.