Can someone explain the value of expertise vs. primary stat/endurance?

I was geared in all War Hero gear pre-expansion.

While leveling on Makeb, a mod lvl 66 piece of equipment falls down. I see that it gives about +45 of my primary stat and +45 to endurance. There is some improvement in the secondary attributes, but I just want to focus on the primary ones. If I use this piece of gear, I lose 150 expertise. I'm primarily interested in PvPing. So I ask, is the bonus in my primary stat and endurance worth the loss of expertise?