Cool list mate, I really like the amount of shots that would fly out of that!
Is the inquisitor just in it for narrative/rule of cool? I'm not really seeing what he/she is bringing to the party yet... Maybe as a Lv1 psyker with divination to ensure you don't miss with your initial scion shooting though...
Why a bolt pistol in the CCS? Have you ever had the chance to fire it? I dearly love snipers, but why not replace them with another autocannon for more range and punch?
Lord Commissar - considered the Blade of Conquest? s4 actually makes a difference when he does get stuck in with marines, assuming that he survives to his I3 step...
What is your plan with your SWS in your platoons - are they a dangerous looking speedbump to keep the assaults on your dakka heavy platoons delayed by a turn? If so, great thinking! If not... are you playing against orks a lot?
Vets = Love 'em, good stuff.
Tanks = Also love them. The Exterminator can have pretty good results, but I do note the actual heavy tank hunting relies on your vets and your scions... so necrons with their monoliths and aggressive land raider bound space marines are going to give you a reeeeeally hard time, either getting close enough to suit their purposes on T1 and T2 or annihilating the squads with all available firepower to stop you delaying those terminators (or whatever they have in there). Considered upgrading to a Vanquisher or Battle tank for the long range tank hunting?
Aegis line = Guardsman's best friend. I don't know why they even bothered with the (awesome looking) wall of martyrs when they already had these to give us optimal survivability.
Don't Scions have Deep Strike already? I don't get why they would be embarked, that just forces you to wait to deploy them.
True but... Inquisitor!
Actually, I 100% agree with Ntaw here. Firstly, never trust a wizard. Secondly, the vendetta is a much better gunship than transport, and unless you really have to, you probably won't want to go into hover mode with it to drop off your dudes. The Grav Chute Insertion is cool and all, but if you are tank hunting with melta then you want to land within 6" of a tank and that means that you have a fair chance of scattering onto it and losing the whole unit... which I have done before and it really sucked. Particularly as in the scenario we were playing, the chaos cultist leader escaped from the prison with his escort and then laughed his way into the governor's palace, since the elite guard were smeared all over the side of a ruin...