For applying Rend via WW/Ambo, both your WW hits and your DD hits are going to stack Rend, so you’ll be plenty fast to keep up 2x Rend all the time that way. When stacking Rend via WW, in fact, it’s basically impossible to be slow enough that you don’t stack Rend 2 or more times per second, even if using the slowest 2H weapon you can find and no added AS anywhere.
But, when hard-casting, you only apply Rend at your sheet APS, which for you is 1.54, not enough to keep up 2x Rend, so that’s a damage loss. That said, it looks like you are not putting AD anywhere, so I suspect you plan on this being a spinning-only build.
You also are forfeiting a bunch of damage via CHD from an emerald in a 2nd weapon. You could make up for a good bit of that with CHC on your shield, but this particular Lidless Wall doesn’t have CHC… did you equip the wrong one?
D3planner doesn’t show what you have in your 4th cube slot… you might want to try putting RoRG there and running Crimson, trading MoC for Lamentation in the cube, and using Morticks rather than Parthans. Crimson now works with S&B, so you may well have the toughness to survive even without BoM, and the extra CDR will both buff your damage and help you to keep your skills off cooldown.
Anyway, looks fun to play with, but I don’t think this is going to be super-duper powerful, especially if you aren’t hard-casting. Good luck!