Blood vs socomm is about an 80 dps upgrade in bis t4 (roughly 4.5%)
But you are ignoring seal twisting.
Double twisting socomm (different ranks) is about a 390 dps increase over just socomm (+23%)
Twisting socomm and blood is a roughly 650 dps increase over socomm (+39%)
Ret will be the top melee parse until some one gets war glaives or blizz breaks seal twisting, and seal of blood is a large reason as to why that is.