...Oh, and since missed this:
You clearly don't have a whole lot of experience using Cyber Subs in high level play. First off, the parry IS a rushdown tool; its purpose is to keep you from getting run over while you're playing offense. Second, it's unbelievably easy to stuff if abused. For one, a lot of contact specials can't be parried, as well as most EX contact specials. Second, low pokes and any normal string that connects low enough on his hitbox can't be parried. Third, once your opponent starts to respect this option, he's going to use fakeouts to exploit you. If you try to catch a jump-in punch, he'll just jump in without the punch and THEN attack. If you try to stuff a dash-in attempt, he'll just rely on low pokes to get you out of it and wear you down that way. Above and beyond all that, most characters will just throw a projectile when they see this coming, and in some cases, that means a full combo punish (Reptile's forceball, Sub's iceball, Ermac's telelift, and so on).
The best way to make use of the parry is to use it as seldom as possible, and to use the EX parry when you do. Realistically, you're only going to fool a good opponent with this a handful of times in one round. A handful of 8% parries has nothing on even one or two parries for full combo damage. Cyber Sub's EX parry is effectively a toned down version of Cage's X-ray.
