I didn't have problems spinning on Mirage. I learned my spins on those blades. I've always heard that 8ft is better for stable jump landings and 7 ft for spins, and I've never used a 7 ft rocker- so I can't compare, but I didn't have any issues with the Mirages.
After Mirage I've gone through 3 other blades: Gold Seals (used), Mid-Level Paramounts, and now Ultima Matrix Legacy. When I changed from Mirage to Gold Seal, I felt my turns got much better, but no difference in spins. Obviously my spins in each blade got a little better, as I've been taking more lessons and practicing more- but after the initial adjustment of 'I can't spin at all' (a few weeks for me...I don't handle change well!) my spins were back exactly where they were, possibly a little faster when the blades are new, but then as I've had a few sharpening, they generally slow down (I love new blades).
Personally I think that angle the video shows is much ado about nothing. We have tons of skaters at our rink in all levels of Ultimas doing everything from Basic skills to Triple jumps.
Mirages aren't a great blade- they are a low level, inexpensive option. If you can upgrade you might get some benefits, but since they come with so many skates, hundreds of skaters successfully learn to spin in them every year. The blade is designed for figure skating, including spinning.
Since you learned spins on a 7 ft rocker, I would guess spinning on ANY 8 ft rocker will be tougher for you.