PapaNurgle's right about the need for at least one counter assault unit though two is a safer bet. Go with rough riders or conscripts (stop'em or bog'em down).
That many mortars is kinda nice... but mortars are more like heavy stubbers for all the good they do. A unit of ratlings would perform virtually the same role by pinning enemy units and would free up a heavy support slot. Ratlings are a better choice against high toughness models and they are more survivable (when in cover). Not that I really like either choice all that much. If I want to pin a unit I drop pie plates on it.What survives is more likely to be pinned.
I'm guessing the real reason you took drop troops was so that you could land troops on objectives given the severe lack of mobility in this force. Minus the sentinels and the Command
HQ that gives you six drop squads (40 lasguns) and one armored fist to make a mission happen.
The chimera will go down early as it will be the only piece of armor on the board. The inf platoon's lascannons become a waste of points if you drop them (average of three turns without shooting and they only hit half the time). The sentinels are bolter fodder.
Begin with 4 free points. Start by dropping the sentinels (that gives you 90 points to play with). Continue by dropping a mortar platoon (freeing 280 points), the
HQ mortar squad (freeing 80 points), and upgrading the other mortar platoon to a lascannon platoon (costing 90 points). You are now up by 364 points
Make the armored fist a standard platoon and give the both the new and old infantry platoon squads heavy bolters. That will only cost you 75 more points (289 left). This change provides increased survivablity (adds one drop squad and one line squad) and makes good use of the points discount.
Add in two 8 man rough rider squads w/ lances for 176 points (113 left). They will secure the lines against breakthroughs.
Buy a heroic senior officer for the command
hq (w/ iron dicipline) and then give a platoon commander the honorific and iron discipline. This costs 40 points (73 left) and forces one drop squad to remain behind but it provides a redundant
HQ. More importantly will keep more of your fragile weapons teams from running on their first leadership check or when they are reduced below 50%.
With the remaining 73 points I would buy 12 flamers for the three dedicated drop squads. Now they can either drop to take and hold objectives or they can fight off infantry that get too close. Flamers are definitely a personal choice here.
New Version
Heavy Weapons 34 (15 lascannons, 19 heavy bolters)
Special Weapons 12 flamers and 16 hunting lances
141 models
Doctrines :
Drop Troops; Iron Discipline
HQ: 1 Heroic Senior Officer w/ ID,CCW, LP
3 Guardsmen; Lasgun (x3)
1 Standard Bearer
6 Anti-Tank Squad; Lascannon (x3)
6 Anti-Tank Squad; Lascannon (x3)
6 Fire Support Squad; Heavy Bolter (x3)
6 Fire Support Squad; Heavy Bolter (x3)
1 Heavy Weapons Platoon
Command Squad; JSO w/ Honorific, ID, CCW, LP
4 Guardsmen; Drop Troops; Lasguns (x4)
6 Anti-Tank Squad; Lascannon (x3)
6 Anti-Tank Squad; Lascannon (x3)
6 Anti-Tank Squad; Lascannon (x3)
3 Heavy Support: Heavy Weapons Platoon (20#, 280 Pts)
1 Heavy Weapons Platoon @ 280 Pts
Command Squad; Drop Troops; Flamers (x4)
6 Fire Support Squad; Heavy Bolter (x3)
6 Fire Support Squad; Heavy Bolter (x3)
6 Fire Support Squad; Heavy Bolter (x3)
1 Infantry Platoon
Command Squad; Drop Troops; Flamers (x4)
Infantry Squad; Close Order Drill; Lasgun (x9); Heavy Bolter
Infantry Squad; Close Order Drill; Lasgun (x9); Heavy Bolter
2 Infantry Platoon
Command Squad; Drop Troops; Flamers (x4)
Infantry Squad; Close Order Drill; Lasgun (x9); Heavy Bolter
Infantry Squad; Close Order Drill; Lasgun (x9); Heavy Bolter
1 Rough Riders
Hunting Lances (x8)
2 Rough Riders
Hunting Lances (x8)
Total cost 1849 points.
This list should be more flexible and respond better to close-in fighting. It will force your opponent to waste his anti-armor weapons on infantry as there are no vehicles or heavy infantry.