Till B grade grade its an easy pick: Bastard*Eleven (or whatever 107), Shamsir*Raid, Tsurugi*Samurai. What about A grade? Are perhaps overenchanted B grade duals with Focus better?
Choices are:
Damascus*Damascus (282) with accuracy+6
Keshanberk*Damascus (275) with 25% HP
or
Keshanberk*Keshanberk (259) with 8% Atk. Speed
Neither seems a no brainer choice for PVE.
most people use OE tsu*sls for PvE, even at 70+.
but the new Aduals with +8 attackspeed have such a high p.attack, I belive they will outdamage even high OE focus duals.
If you consider a Kesh*Kesh +4 then there is no question... even decently OEd Tsu*Sls (>= +8) will give you a higher DPS with lower operational costs. So if you already have it stick with it.
Comparing with the new A dual, a Dama*Talum +4 DPS will be higher than any Tsu*Sls below +16, but if you have a higly OEd tsu*sls (like >= +12) stick with it for PvE. It will still give you a lower DPS than a Dama*Talum +4 but will consume SSBs instead of SSAs and consume less Soul Shots overal.
If all you have is a low OEd Tsu*Sls, then you might consider going to the A grades, te highly OEd Tsu*Sls are significantly more expensive atm, you would hardly save enough on SS to compensate the difference.