Hell of a lot of non-obsec troops with not much hitting power
imo. I'm really not a fan of the orbital strike force - the bonuses don't make the
tac marines worth it. Bear in mind the reroll of ones only works on wounds not
AP rolls, so not much use on those meltas.
I'd be wanting ditch the SOSF for a Shadowstrike
KT and moving some of those scouts over into that formation. Gives you a bit more hitting power. Realistically you only need one scout squad in the Pinion to give the
devs ignores cover - the others are better replaced by Pods for the
tac squads as
DS > outflank
imo.... And then you're better off taking a regular Demi
BC for obsec rather than ignores cover on a single unit of devastators (just take a
WS librarius if you really want that, but I wouldn't bother).
In my Talon
SF list I run a Demi Company with grav centurions and podded grav tacs, a Shadowstrike
KT with 3 scouts squads, a Raptor Wing (unfamiliar with the air superiority detatchment) and a UM conclave with Tigurius. To get it down to 1500 I'd just drop the conclave and put more into the VG vets
Edit: taking a regular Demi Company would also allow you to take a Cataphractii Terminator Captain. Put him in the devastator unit to give them
SNP 
far more useful than the chaplain