The reason for your new threat issues is probably not your new gear, but your dps' new gear.
One issue we have in this thread is a problem of misunderstanding an abbreviation.
RS is Rune Strike. It works on your next melee swing. This is *NOT* an RP dump and is not on the GCD. This is an ability triggered when you dodge or parry.
Frost Strike, or FS, is the Runic Power dump and should be used at the end of rotations or for RP bleed off.
Macro Rune Strike into all of your strikes(PS, IT, BS, DS, OB, SS, HS) so it will get weaved in.
Regem everything you have from hit and defense to exp/stam due to the double benefit exp gives you. If your defense is still 540, change your sigil to something like Sigil of Deflection or Sigil of Awareness, because your sigil currently isn't as big of a benefit as it could be.
Once you are capped expertise, get your hit up, but you should be fine with whatever you get form gear and can stack more dodge.
I've changed my gems, but my expertise is still only 9 (40 rating). Is 60 rating the cap?
Being expertise "soft capped" will help with threat. Getn hit capped isnt as important and u seem to have a healthy amount. You could enchant ur gloves with expertise or armsman. I would re-enchant ur chest with Def so you remove the Def and parry gems with more useful stats like stam/dodge.