I think the HQ body is for the higher double/triple meld chance. While Cobalt Haubergeon might be the better body choice, as a practical matter the stack of HQ bodies you need for double/triple melding might dictate going with the Tortoiseshell armor instead.
Once you can go above STR/PIE caps, then the question is how does Crit gear stack up? Especially after last patch I don't know the answer to this.
Can you list your gear set? Since you are above the STR cap (I assume) you might be better off with a Crit Atk body.