What is the point of Expertise rating on gear?

I understand that, but it seems to me that this is a problem that could easily be fixed with proper stats itemization. For example....

PvP:
Gear should be very Endurance heavy with secondary emphasis on core stats (strength, aim etc..)
PvE:
Gear Should Strongly emphasis Core (Aim, Strength) and Secondary (Surge, Alacrity etc) stats.

You then would have two very different gear sets people would want for very different reasons. Your pvp set would give you the survivability you would expect from a pvp set, and the Pve set would allow players who wanted to raid/pve get the most out of the important raiding stats. No raid is going to want a dps with a lot of health that cant push out the numbers another dps could. And while having a big emphasis on core and secondary stats does not necessarily discourage people from pvping, I think one could make the argument that in terms of organized pvp it would be far less competitive.

And if that was intended behaviour then the optimum PvE raiding gear would be a mix of Rakata and BM as well. That is not the case.

Not really. MMO is based on improving your character. I will just play guildwars, twink at WoW, or play warhammer free trial if I just want to pvp and not get any progression.

Unfortunately, this isthe truth. A person in Full Rakata gear is more powerful, in PvP sense, then a person in Full BM Gear. BW needs to increase the diminishing return on expertise to start around 20%.

If you simply stack endurance on PvP gear, then the problem becomes PvE tanks feel that they have to PvP in order to get the gear they need to raid with. You get the same problem, but in reverse.

That might be the formula that WoW PvP works under, but it's far for necessary. GW was very successful with the PvP character system and GW2 is also following suit. DAoC also had very little progression once you got over certain RR humps. Not to mention that grinding for PvP power progression was one of the things that utterly broke Warhammer.

That is correct if you are only taking into account endurance and comparing them side by side, but as I said before by itemizing raid gear appropriately and properly utilizing your secondary stats in this case defense, shield chance and absorb your effectively take a tank with less health than his pvp counterpart and ramp up his mitigation so he would be taking far less incoming damage than a pvp geared tank.

The trick obviously would be in determining exactly how much of the secondary stats to allow the pvp or pve gear sets to obtain. Then compare your tanks side by side again.

Give it up. Your idea sucks. Everyone keeps telling you that but you are not listening.

Simple solution, make PvP gear only usable in PvP zones, make PvE gear only usable in PvE zones. Problem solved. then your PvP gear can have whatever stats they throw at it and not affect the PvE game, and vice versa.

You want to PvP? Get PvP gear. You want to PvE, go raid with your guild.