Well, if expertise rating is 1:1 to spell dmg at 825 TPS and better with more TPS then if you are making that much (personally it seems a bit high to me too but it will still be high regardless) then the expertise is gonna be a lot better.
BUT
I was thinking about this too, getting the legs that is. Note that you will get expertise dodge capped from your passive 10 expertise skill, the neck, cape and ring from sunwell (ok so maybe the cape and ring are not available to you but the neck is), anymore will have its effectiveness halved as you are only reduceing boss parry not dodge and parry. In this case expertise will even out with SD at a much higher TPS threshold.
However, after rereading your post I noticed that you already had them. In this case I would use felfury for single target tanking until you started getting enough expertise from different sources. I have the neck and I'm at 17 expertise, the dodge cap is about 26 and parry cap is much higher, about 60-65 (assuming around 15-16% parry, anyway...), so 2 items will almost cap you and the 3rd will (although the ring is sick for normal tanking anyway, the threat is a nice bonus).
Once you hit the dodge cap the 47 spell dmg is better.
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