Magnification is a little like money... you can rarely have too much of it
Some people hate mirage; they feel it distracts them too much as they can't see the target clearly. It certainly does add a noticeable degree of eye strain and subsequent fatigue to the equation. Others hate not being able to clearly make out the edges or lines in a target as it gets all squiggly. I know I used to hate trying to shoot prairie dogs when it looked like they were out there doing the moon walk in the heat waves ;)
Then you have the other camp; mirage is there, whether you can see or not. Just because you back off the magnification to where you can't see
the optical distortion does not mean the heat waves are not displacing your target image from where it is in reality. More importantly, mirage shows you the wind - often people refer to mirage as 'wind you can see'. If you can see
the mirage angling up and to the right across the target... it shouldn't come as too much of a surprise when you have to hold a little low and left from your zero to actually hit the center of the target. Likewise, if you see the mirage (wind) suddenly flip the other way (up and to the left), you know you better hold off to accommodate the condition change. How much depends a lot on the individual range and its layout, but hopefully you get the idea. I've had situations where I was having to hold off as described to hit the center, and it was driving me nuts (didnt click off, as it wasn't quite enough to merit that much compensation). However when a breeze would dip down across the target face and blow off the mirage for a few seconds... I'd literally see the target 'jump' down and left - surprise, surprise.
As I said, mirage can be your friend - it tends to be more responsive faster to small changes than flags which have mass and take longer to show, or may just flutter in a quick little shift in the wind. Too much mirage can drive you batty, though. I've shot where there was an asphalt shingled roof over a firing line down range giving off horrendous mirage... enough so that the gun was wobbling slightly one way, and the mirage image was wobbling far worse going the other way. If I was more susceptible to motion sickness, I'm pretty sure it would have made me puke!
The 5.5-22x will work just fine, especially if you get a fine crosshair like the NP-R1 or R2, or one of the CH reticles. Perhaps even w/ the 2DD... just anything that doesn't cover a lot of real-estate on the target. I think you'll find that the 42x scopes allow you to refine your call much tighter... shots that you would have called 'rock-solid' and had no idea why it ended up in the 9 (or 8) ring will look a bit less steady... and you just may see your last split second 'jerk' or flinch that sent that round off for the back 40...
FWIW, I hardly *ever* turn down the magnification, and I know I'm not the only one who shoots like that. Other people like to turn the magnification down to where the worst of the mirage goes away and the image stabilizes, but they can still see shifts and let-offs and pick-ups and such.