For a reliever it is. Average FIP for starters is 3.91, for relievers it's 3.66. His walk, K and swinging strike numbers are far below average for relievers.
The game plan looks to be swing early and avoid getting behind, Sale is nasty and you don't want to face him with two strikes. Can't disagree with what the hitters are doing here.
Not really, Sean Doolittle is another pitcher who throws his fastball at a very high rate (86.6% of pitches in his career) and he gets a substantial amount of swinging strikes (13.2% SwStr).