I have both shafts, Ex Pro and WX Sigma (12,5). Both shafts are not pro taper, but very close to pro taper. I did not measure them, but I clearly can say that both feel great when playing with closed bridge. I'm a big fan of pure and long pro tapers like the cynergy shaft 12,5 mm, wich is my absolute carbon favorite shaft. The Ex Pro and als WX Sigma 12,5 mm play and feel to me very similar to a pro taper.
For a better relation and understanding for what's feeling good to me: Over the last 2-3 years I mostly playes IQ infinity 12,7 and cynergy 12,5 , and at all infinity shafts (I have 5 of them) I had to sand down the taper a little bit because the original taper was already too conical to me.
At the Ex pro I do not like the sound, which is some kind of hollow to me, and all the tips that I was used to came out too hard in the Ex Pro and the sound was nt nice, this is why I preferred only the Ultraskin Pro ans SIB Pro, which were just about acceptable. I had a couple of different Ex Pro on different butts, and every time it was the same thing with sound and tip. The playing performance of Ex Pro is very good, nothing to complain about.
The WX Sigma instead is a shaft that has a really solid and very natural and consistent sound. It plays great in all different situations with very little deflection. The stiffness of the WX Sigma 12,5 I would call as medium stiff. All in all an absolutely great shaft, I love it. I play it on my old Meucci from year 1989, never had a cue that feels such great, to me the best combination I ever had.