Ok, so, I did another run.

Turned off raytracing.

Turned off light through transparency.

Accuracy set to 1 pixel, antialiasing set to good.

GI set to Excellent, 4 Pixels

Render time, .......

12 minutes.

No doubt the quality is affected but you can assess it for yourself.

Another thing to note is that I have re-saved these images with JPG compression set to 20.  So, some of the artifacts you may be seeing is from that compression.

-Kix