Actually, if the 3.X rotation beats the 4.0 one in pps with a Thundercloud proc, and the only potential drawback is us "catching up" to the Foul timer...
Now that AF and UI are 13 seconds...
We should not stack speed and use the 3.X rotation.
We stack DH/CH to make sure each spell hits as hard as it can. We have more AF/UI time now, so we don't need as much speed for the 3.X rotation. And this also makes sure we'll get a hard-hitting Foul when we get to UI.
We do the B4+8xF4 opener to get Foul ticking like 10seconds ahead... and then we go into 3.X mode, until Triple and Ley Lines are back and we use B4 again to, once again, get Foul a bit farther ahead again.
We Sharpcast T3 to get the most TC procs, so we further extend the timer (we can use these in AF without loss for the 3.X rotation, unlike the 4.0 one...).