I like the changes, as it will open up into a more in-depth system and allow for much future expansion. But... part of the appeal in this game was the fact that you never had to min-max. With this system, it just sounds like you are going to have a ton more min-max type behavior, where having the correct set of gear is going to be that much more important (especially with the "hard mode" objectives attached now to instances).
I also disagree with the manner in which these values are presented to the user. If the rating is broken down into percentage points in the tool tip... why don't you still display the percentage points and just keep the rating internal? You can mouse over the percentage and see the total rating and how it is broken down due to gear, traits, and basic stats. To me, the character sheet should display the simple output (percentages), and if you want more information, mouse over the percentage (rating breakdown on percentage contribution).
I completely get the reason for the changes and support them. I like having a more complex system where I won't just throw away that piece of quest gear, and I'll have to decide on whether I want more mitigation in one direction over another. But, I really dislike the new presentation method for the system. It just seems backwards and unnecessarily complicated for quickly seeing the effect of changing gear.
Now I swap gear (mouse over the item in my inventory), I see the rating go up in my character sheet. But what does it mean? Ok, move the mouse back to character sheet to see how the new gear changed percentages. Wait, what were my percentages before? Better put the old gear back on. (Move mouse over to inventory again.) Ack! Lost my tool tip! I better get out some paper and write down everything before and after.
You can no longer just swap an item out and see how the percentage breakdown will be influenced by the change in gear. It appears that display mechanic has added a lot of extra work. I like the min-max gear game, and I can already see myself saying forget it, since the interface will just get in the way of achieving my goal.
Give us back percentage ratings as the display mechanic, with the overall rating and appropriate contributions in the mouse over. Split the character stat UI section into two parts (base stats with crits as part 1, and resistance/mitigations as part 2), if you cannot fit all of the new percentage ratings on the screen at once.
There is way too much work involved in constantly checking tool-tips to see how something changed.
Anyway, I'm sure I'll get yelled at by someone for saying this, because I "haven't actually used it yet." Well, I don't need to hold a chicken in my hand to know that I'm looking at a chicken.