Alright here are my views but i'm fairly new as well
HQ is fine, Not a fan of vox networks but thats a playstyle choice, as are the Psyker. Also don't normally go for the cross, lots of points for a higher save...he has enough surviability by his squad dying before him that if those go some minior save isn't going to help much imo.....i may be wrong though. Depends on how you use him, mine stays back, you may be more agressive.
Snipers are generally agreed to be a fairly poor choice except vs nids and some of the necron monstros creatures. Also ratlings cost less per sniper rifle and get better cover...take a doctren though. Not a fan, but they can work, and snipers are cool because there snipers.
The sentinels are not grouped logically, they count as a unit and must move together. So you have a flamer sent grouped with the long range autocannon sent. I operate them in one man teams that way they can seperate, target seperate, and when shot at a unit can kill a maximum of 1. I know you can only fit one slot here, i would add one to the fast attack slot, and make the remaning 2 of the same type or reduce to one. For the fast attack i would seperate the 2 into 2 fast attack choices. Use all your slots.
For elites, i don't agree with how you have set up the vets. the honorific may be wasted here, also your spending a lot of points on a single model that is not that great, he is ending up costing a lot and still has worse stats than a marine.(save wise and such)
Personally i would keep him cheep as there job is to infiltrate(or drop), unload death and be a pain...once in close combat there dead, a better save and a few wounds are not worth it imo. Also your mixing weapons, you have a melta a plasma and a shot gun? I would put 3 of the same in the squad. 3 plasma is shooty death for marines, Melta's is almost a garanteed tank kill if in range. Don't mind power weapons as there cheep and at 5 points if you kill something your units done good. But i would not expect them to charge in and come out on top..
Storm troopers at least have a better save, if your heart is set on a 3 wound model w/ power sword, put it here. Not the best choice but if for flavor go for it. Bombs are fine, if you have melta bombs maybe go with plasma? unsure on that advice.
Not sold on the plasma pistol for the junior officer he can die shooting it, he will only shot it once(short range, after that he will probably be assaulted or assault. I may chang ethe melta to a plasma as this works better with the HB. the melta is anti tank, the bolter anti infantry. the plasma is anti marine.
For the second HQ..who has the powerfist, the officer? if so i'd down grade to a PW, but that just me.
Also unsure of grenades for all.
Fast attack i would split the sents into 2 seperate choices.
For the tanks i would be tempted to drop the lass cannon and get a bolter, so you have all bolters...
On the flamer one i may go bolter but i have never actually seen that used.
For the demolisher the multi melta may not be best, the demolisher is awsome at short range, when it is out of range it's useless, by giving plasma is has at least something to shoot at things farther away.
you also have 4 heavy suppport slots, believe you only get 3. Also the basalisk should have indirect fire. it should then be hidden behind cover and blow things up, it should not really get shot at till late game when things come around the cover it is hiding behind or something deep strikes to kill it. Thus the armoured compartment may not be needed.
Hope this helps but rember i'm new and it apears i play much much diffrently than you. I tend to shoot where your force seems to be more for CC.
I also notice a lack of las cannons, can SM field any 14 armour? or will the missle launcher beed good enough?
For advice, the post above is decent. Rough riders are great. but i just found out they are very specific. they are counter assault.
the best advice for guard i have heard was.
As a shooty force you start off winning the game, you kill more of them in shooting for the first turns and everything is your way at the start of the battle(everything far way,units won't be in close combat till turn 2). After that you have 6 turns to not lose the game.
Also guard can be hard to play as they are not as forgiving as space marines. (oh no my shooty squad got assaulted...whew they still kick but in assault)
Also deployment matter a lot for the guard. other armies move forward to get into CC....guard typically have a large portion of the forces remain still so where there set up is where they stay.
I look forward to your battle report.
And yes model vs model marines win...thats why you bring twice as many.