Few flaws in your logic sir.
Your example of 10k dmg to a 30k health pool, and then 25k to a 90k health pool. From what I can see damage isn't doubling, not even close. Most classes are doing just a little more than they are doing now with what gear has been found in the beta.
So yes, 10k damage to 30k health is a bit crazy right now
but 14k damage to 90k health, is a bit more how its..basically always been? level 60 geared rogue crit for 600 average, thats an average. and most people in vanilla had what? 5k health? not much difference just bigger numbers.
Second, combat ratings are going up more than they ever have in an expansion
From 60 to 70 crit scaled 14 crit rating = 1 crit to 22 crit rating = 1 crit at 70. A marginal change honestly.
From 70 to 80 it went from 22 rating = 1 crit to 45 rating. This was a big change, more than double the rating.
now take a look at how much you need for 85.
179 crit rating for 1 percent chance to crit. almost 4 times more rating needed, and ALL combat ratings are like this. and from what i can tell from the current epics that have been found, there isnt 4 time more of anything other than stamina. stamina has basically no budget now thought so once we hit raids health pools are going to start sky rocketing and damage is going to be slowly going up in comparison.