Is it just me or was Scarif the best posting a storm trooper could get? Nice weather, awesome beaches and it's a top secret facility so little chance of getting in combat*.
Compare it to, let's say, tatooine wich is hot, sandy, and you'd better turn a blind eye to what the Hutt cartell was doing if you knew what's good for you. And don't even get me started on what artic hellholes that snow troopers had to go to.
I'll take the tropical paradise data storage planet, thanks!
* yeah that didn't work out so well.
Was it top secret though? I didn't get that feeling really.
And backwaters like Scarif is where you put the incompetent, the recuperating, the dead enders and the expendables. If yoy want a career you don't want to be there.
From the MorofTM and scarif stormtrooper squad leaderTM action figure pack: "Specialist stormtroopers stationed at the top-secret imperial military headquarters on Scarif."
My tought is the emperor ordered some imperial admiral/general to build and then assume command of a secret HQ to store all their sensitive data and the guy had free pick of all the imperial worlds, so he got clever and picked some backwater paradise planet so he could serve the empire while surfing and lying on the beach in his spare time. (Hey, it's what I would do.)
I think it's more of a place where you get promoted to after serving the empire loyally for a long time, sort of like retirering on the Seychelles. 