hey,
first i can recall razorbacks carry a maximum of 6 models and cannot carry those troops i would give them the rhinos from the sterguard and put in 2
dps in place, i do this and i have lost once in about 25 games. On top of that you deffo don't need
PF on your sergant of your squads, it's a waste of 25 points, i would replce them with a
PW so you have another 20 points from both of them and another 20 from the razorbacks.
Again
PF on the sternguard sergant i really think you don't need them so either peplace it completly with 5 combi- weapons or 2 combis and a
PW. since you still have 40 points from the tacs you can boost your combi-weapons to 10 on both of the squads, this will give you the awesomnness to blow a hole in any taank when you come down and if you combat squad them either combat squad them a kill 2 units! also when you combat squad them you get another scoring unit. with regards to only 8 sternguard best boosting that up, leadership and survivabillity. so i would say if you drop both powerfists from the tactical squads i would say use that 50 points to get those two guys.
I think, for your extra 250 points i am loving the marines but 1 alteration, pistols can count as extra
ccws so you only need to take a
LC and with that 15 points maby a plasma pistol on oone of your other dudes (saves your sarg if you roll a one on to hit)
heavy support, vindicator

predators,

heavy bolter is no good, if your not gonna have las cannon sponsons over
HB i don't think it's worth it, i can maximumly take a low
AV tank out with it's S7
AC. i say remove them or a least on of them and find the points either for a pred with
LC sponsons or another vindicator, 2 vindicators is mean. say you get anothe vindicaor and you remove both of the preds you have 55 points to spend.
altogether you get:
75 - removing
PFs
-50 - two guys
170 - removing 2 preds
-115 - vindicator
20 - replacing razorbacks for rhinos
_____
100 points left, i would spend it on upgrades or a thunderfire cannon, that way get a servitor aswell for all the tanks.
thanks,
madman12367