If the Sentinel just does a HSF without any prior attacks i.e. a fierce or a rocket punch, just super jump and you should be fine.
If Sentinel does a fierce or fierce xx rocket punch xx HSF, push the very last attack prior to the HSF. I do not use the drones or the change in color of the background for timing. After any attack Sentinel does before the HSF, there is a tiny gap of empty space while the rocket punch is retracting or the fierce is dissipating and the drones are on their way. During this empty space, pushblock. Your character is still in block stun due to the previous attacks so don’t worry about being hit by the drones. Put the joystick to neutral and wait until immediately after the second set of drones, at this point, manually super jump and your character should avoid the third set of drones. This tactic works with most of the characters I have tried it with, namely Magneto, Storm, Cable, Psylocke, Iron Man, etc.
A few fun but very risky things to try with Cable are to normal jump prior to the HSF and pushblock, once the pushblock timer runs out, AHVB. The drones should fly through you and you are free to AHVB until your meter runs out. If you are quick enough, you can AHVB instead of super jumping out after the second set i.e. PUSH -> WAIT -> TKAHVB -> DEAD SENTINEL
With Storm or Magneto, after jumping out of the HSF immediately dash to get right on top of Sent you should be able to land a falling fierce into whatever with both characters, if you dashed quick enough of course.
With Sentinel, you can activate flight and fly forward and do some combo with some roundhouses and some assists and some rocket punches. Usually roundhouse + assist, rocket punch. There are some other things to do but I don’t feel like getting creative right now.
There are a few preventive measures a Sentinel can take though with HSF. Usually dropping Doom’s AAA or Blackheart’s AAA or even Storm’s Proj. will keep you grounded when you can usually jump out. But, there is also a counter to this counter. The usual pattern of FIERCE -> ROCKET PUNCH -> HSF has a lot of gaps which can be jumped out of, usually the assist dropped during the pattern only prevents one or two of the gaps which just happen to be the most popular gaps to jump out of. So, test the waters and see if the Sentinel you are fighting is keen enough to drop an assist during the first set, if they don’t it is safe to say they won’t try it later and just jump out at the regular interval. However, if they do drop an assist don’t jump at the usual gap, try a different one.
I have not tested any of the timings for the other gaps so it would be best for you to turn on training mode and test it out for yourself.
So, if you have anything else to add, such as the timing for Sentinel to jump out (it seems to be different from what I use for regular characters) or any other strategies involving this post up.