The problem with Sheer Force is that Crush Claw can miss and the lack of LO recoil is about as big of a deal as potentially missing, Rock Slide hits nothing important your stabs don't, and Brave Bird doesn't care. Since Brave Bird/Return/Superpower is the best coverage to begin with and doesn't not hit anything neutrally (the only thing you REALLY want to hit that those don't is Bronzong, anyway). Roost and U-turn are so much more useful than Rock Slide ever is as well.
I have gotten randomly bopped by life orb sheer force Heat Wave (which takes 116 special attack just to 2hko mega steelix, which is sad because it only really hits two big targets), while Defiant lets you really punish your opponent for daring to remove hazards, carrying an intimidate mon as a key part of their defensive core, having to rely on potential drops to get a kill (Aromatisse's Moonblast), and so on.
It seems interesting on paper, but the lack of useful moves to take advantage of, plus the already decent base power of existing moves that don't, makes it kind of useless in function.