(TP_B*Delay_A)/(TP_A*Delay_B)*100 will show you the ws frequency increase of adding Dual Wield vs the original Delay/TP gain. The only time DW hinders performance is when you're relying on OaX since it slows the swinging. But even then, the gains are higher than 10% DA from /WAR.
Same scenario as before, 200 Delay weapon, and 2*200 Delay Weapons.
Delay A = 200
TP A = 5.4
Delay B (after factoring DW3) = 300
TP B = 4.7
4.7*200 = 940
5.4*300 = 1620
floor(940/1620)*100 = 58% increase in WS frequency. That's from 0 Dual Wield to 35%
DA% increase in WS frequency is 10/100*100 = 10% assuming you're adding 10 onto a value of 0.
Dual Wield stomps all over DA in significant additives.
0 - 180 5.0 + [(Delay - 180) * 1.5 / 180]
181 - 450 5.0 + [(Delay - 180) * 6.5 / 270]
The above are the two values that'll apply Dual Wielding. You won't see a huge reduction in TP/hit unless your combined Delay falls below the previous bracket, in this case <180.
Edit: Sanguine Blade is pretty nice honestly.