If you're already soft capped on expertise, which is not that hard to do with all the expertise loaded on tanking gear, then the effectiveness of the 10 free expertise is halved when looking at tps generation. Also, once you have the full vengeance/corruption stack the tps boost from expertise is further reduced as you're only doing a few extra seal holy damage with each weapon swing.
Don't get me wrong, I think Vengeance/Corruption is a great tanking seal. I'm just not yet convinced that it's our only option, and given the correct spec/gear choices it may be overshadowed by Blood/Martyr enough to warrant at least using them situationally. At the very least, expertise from gear and speccing into reckoning gain a much greater benefit from using Blood/Martyr.
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