Just be wary that you can be hit out of the dashes. For that, mix up your dash A a lot as opposed to only doing them when you're out of reach. If you're out of reach for another A and think they're going to hit you out of a dash A, keep them honest with a 5B or 2B.
Like Tempered said, F-Sion has 3 overheads and since her staggers are her strongest asset, you can mix up the overheads just as well as the H and C moons can. As for the canned blockstrings, I agree 100%. Avoid the habit of thinking stuff > 5CC all of the time is a good idea because it's not. If your opponent is an idiot, then sure it's a good idea. You can jump between the 5C and the pull back, which a decent player will most definitely know.
If you use gunshots or 3C to make them hold still after 5C, you can force them to respect 5CC. Just beware of characters that have a DP because that's the one thing capable of beating that frame trap (*gasp* frame traps aren't unbeatable! Mind is full of fuck!) and nothing is more salt-inducing than letting someone like Nanaya or Roa get out of dodge by DP'ing your follow-up.
Another honorable mention is 22B. This is quite the opposite of abusable because it works wonders when you rarely use it. If you toss it in during a block string, you'd be amazed how strong the "Deer in Headlights" effect is on some people. Again I would advise against using it a lot as it's easy to disrespect in many ways, but it's great if you toss it out on a very rare occasion.
I also can't stress this enough, but don't be afraid of using throws in mix-up. In high level play, I'd be a little more conservative with throws in case they're doing the A+D OS (if that still works), but it's still an available option if you feel like your opponent is a little too comfortable with blocking. Sion's throw doesn't do as much damage as you'd want it to, but throws in general can do a lot of psychological damage to the other player if they let it bother them enough. In other words, throws make it possible to annoy them into making mistakes because you're still opening their defense in some way.
I'll post more as I come to think of it, but that's what I got for now.