Siren.Corrin said:
http://wiki.ffxiclopedia.org/wiki/Azure_Lore:_Kyte's_Guide_to_Blue_Mage#FAQ A few questions down there is one where he mentions Disseverment specifically and gives numbers. But yes, if you have subtle blow, the mob will get less TP from the spell than if you did not have subtle blow.
Fantastic, I thank you for posting your source sir!