Hi there Cossack, Welcome to IGMB..
Now looking over your list:
As stinckpickle (sounds nasty) says, you only have 3 autocannons that you can use to de-mech your opponent with.. LRMBT shouldn't be used against armor, they should fire at infantry eventhou they are ordnance.. Demolisher can be used at heavy armor like Land Raiders and Monoliths, but again these should be used against infantry (heavier infantry that LRMBT ofc..) So you seem to be lacking in long range high S fire power..
Luckily you have alot of room for heavy weapon and 1 place that has all the points you will need to get them..!
Yarrick.. Get him out of the list.. He is the biggest point sink in the codex, and dosn't give ANYTHING to any list that can't be found better or cheaper somewhere els.. That frees up points for what you actually need..
All infantry Squads should have the following: Autocannon and Grenade Launcher (but actually dosn't strickly need a GL) blob the squads 20 and 20 and put a Vox in each..
Now that is 8 autocannons more you have just added to your list.. so you still have more than 100 points left of the Yarrick incident..
Platoon command squads.. Right now they are not doing anything.. You can keep them that way and use them as "grot-squads" for objective grabbing or you can give these.. Hmm.. Autocannons! Yay! More dakka dakka.. + You have the ability to give orders with the PCS to the infantry squads to make them survive longer (Incoming!)
So Now your list is Tanks in the back, infantry inbetween.. Shooty Shooty Shooty.. Fair enough, lets make the shooty better than.. Orders from CCS.. Drop that powerfist, it is waste of space on such a small unit, if you want CC then you have to take Straken.. Get 2 CCS because you will need the amount of orders, give both a Vox.. Now these units also have BS4 so a high S long range weapons could be usefull, but would make people shoot more at the CCS (which you need for orders) so it is upto you..
Both the PCS and CCS btw. can also be kitted out with melta or Flamers to be a deterent to DS and assaults, but you know your opponents better than I do, so i'll leave that upto you..
Mortar squad.. Mortars work.. But you need large numbers of them to work.. So personally i'd find the points and upgrade them to more Autocannons..
Now if you feel that there are too many autocannons, you can allways change some of them to missile launchers, just make sure it is the ones in the infantry squads you do this to, because they are better protected..
Heavy Support: Wow you really like you tanks..! Good Man!
Well personally i'd say it works quite okay the set up you have going.. I would trim away the Lascannons on the hulls, because of BS3 thou.. Same with the stormbolter, which seems abit strange to be honest.. That gives you enough points for a set of plasmasponsons to put into the first squad of lemans.. (or whereever you might think they are needed)
Then if you still have points left, i'd put flamers in all the infantry squads, to give them more of a punch if stuff gets to close..
That turned out to be quite a slab of writting..
Hope some of my mad talk helps..
Kras..