Why all this points wasted? gargoyles are just moot, imo. TL heavy bolter is too costly for what it does, havoc launcher is useless due to movement (you can't snap fire it so...will you stay put to shoot that?) daemonic possession can eat your models alive...nope!Warpflame Gargoyles, Hull-mounted TL Heavy Bolter (20 points), Havoc Launcher, and Demonic Possession.
Remove said things and add bodies on the rhino units
(one can go to 10+1 meltagun, the second one can go to 9)
Just take the thing with the scout shenanigan.
You should also be aware that 8-10 marines are not such a fearsome enemy to face in assault. 20 cultists could be more threating on the charge... i think you lack a dedicated assault unit. Maybe one rhino could have khorne marked marines for some more attacks?
Also, are you shure that landy is accessible to chaos?