If it is out of focus at max power then it is also out of focus at minimum power, it just doesn't look so. But the parallax is still there and if you can't focus range the close targets accurately you are going to miss a lot of small kill zones. To me the inability to focus at 10 yds. (as claimed by the manufacturer) makes this scope unsuitable for FT.
If your 124 is tuned properly at 12# I would consider it mild. If it is not tuned well and the piston is slamming into the front of the compression tube it can damage a scope even at 12#. But Athalon claims a lifetime warranty and I didn't see any disclaimers on air guns.
Charter member of Over The Hill Gang