if that is your outlook on the 4 tanking classes, then you are already beyond help. A dogmatic view of which tank is better is either a way to avoid trying to do better, or a way of simply whining.
Let me ask you something.
Have you struggled thus far?
If you answered yes, then you can stop reading and continue practicing.
If you answered no, then you can continue reading and I can say that you probably know what you are doing, and I can tell you now that... no this is not a huge nerf.
Mathematically the change in frost presence does not do much to your EH.
IBF's Cooldown was increased by a minute. Fine, that's a change I'm willing to take due to the array of other cooldowns we already have.
The change in toughness is something that I expected to happen. 5% less armor is less of a nerf than our previous frost presence nerf which ALSO contributed more damage... but very little. This one is fractions of that.
If it's a nerf to you, then you are lost.
It's a class change... Death Knights, regardless of how long this game has been out, are the newest class to WoW, if you did not expect class changes, then you haven't been playing long.
And I apologize for the caustic nature of this response, but as a lot of people know, I hate hearing the word "nerf"
Aside from that, it's not a big change to the Death Knight as far as those mechanics are concerned... I'm not exactly thrilled about having to spec yet again... i hate it when I do that, because I always end up paying 50 gold anyway for that one stupid talent point I accidentally spent in the wrong place.
But if you're a tank, do what the other tanks do, rather than say, "yep we're nerfed... that tank is better than me..." Try to work around the changes... which are small anyway, granted I'm not particularly thrilled about losing 3% of my stamina, but it's not major. The other trees don't even get a stamina bonus, so you should be happy that you get one at all.