Looking at the Tier 4/5/6 values on the front page and comparing them (a bit off because Tier 4 apparently doesn't include BoK, so I took the strength and agility values without agility and for the Tier 6 agility value subtracted 10% which should be close to its value without BoK):
Tier 4 Tier 5 Tier 6
Attack Power 1 EP 1 EP 1 EP
Strength 2 EP 2 EP 2 EP
Agility 1.74 EP 1.8 EP 1.52 EP
Crit Rating 1.97 EP 2 EP 1.74 EP
Hit Rating 1.34 EP 1.4 EP 1.69 EP
Haste Rating 1.28 EP 1.48 EP 1.82 EP
Armor Penetration 0.22 EP 0.28 EP 0.35 EP
Expertise Rating 3.18 EP
Lets look at the percentage difference between them (using Tier 4 value as a base line):
Tier 4 Tier 5 Tier 6
Attack Power 1 EP 100 100
Strength 2 EP 100 100
Agility 1.74 EP 103 87
Crit Rating 1.97 EP 102 88
Hit Rating 1.34 EP 104 126
Haste Rating 1.28 EP 115 142
Armor Penetration 0.22 EP 127 159
Expertise Rating 3.18 EP
Looking at the difference we can see the following:
Comparing Tier 4 and 5: Relatively small difference in haste rating (+15%), big difference in armor penetration (+27%)
Comparing Tier 4 and 6: Relatively small difference in Agility and crit rating (-13% and -12 %), big differences between hit rating (+26%), haste rating (+42%), and armor penetration (+59%).
I can't compare Expertise Rating because there aren't any values for Tier 4 and 5 in the opening post.
So from that we can gather the following: The EP of AP, Strength, Agility and crit rating stay relatively close to each other. Hit rating and haste rating only change in a significant way when you reach the Tier 6 EP. Armor Penetration sees the biggest difference in EP.
It would be nice to see what values were entered to get the Tier 4/5/6 EP in order to check the following:
Why do those EP that change signigicantly doso, is it because of all the values or only because of one or two values (for example the change in Armor Penetration could quite possibly be because more armor penetration was being worn when getting the Tier 6 EP in comparison to Tier 4/5).
What I'm trying to get at is the following: Would it be possible to assign a fixed EP for those stats that stay relatively unchanged, while only checking a few stats for those that change significantly. For example saying (arbitrary numbers): " Armor Penetration has a value of 0.22 EP. For every 100 Armor Penetration you are wearing add 0.05 to its EP." And so on.
Note: this is relatively unpolished and not entirely thought through and there are probably many things wrong with it. However, I first want to see if this approach is even worth pursuing before sticking a lot of work into it.
The goal of this approach would be to make it easier to get your EP values (since they do change to a certain amount accordingto your equipment). Because from experience (and reading this thread) it is quite obvious that many people have problems getting their own EP values. In addition they make a relatively small difference in item selection (as Malan noted, except for a few items, changing the EP values doesn't change the sorting of the items effectiveness too much). Using this approach could yield something along the lines of only having to check/enter a few numbers/values/stats in order to sort items correctly (for example only checking how much Armor Penetration I have in order to correctly wigh Armor Penetration).
Feel free to tear this post apart.