Given that a new edition is out in about a month, it's a bit difficult to give lasting advice, so I'll just pick out a few things in case you end up sticking with this edition:
The
FAQ (
linky) for the main rulebook restricts Relic upgrades to one-per-model, so you can't stack all three on your Company Master.
Meltaguns do their best work up-close, getting the extra dice for penetration, so foot-slogging them (taking them without transports) is generally inefficient. I'm presuming you're planning on combat-squadding the tacticals? In most scenarios having a transport for a tactical squad is best - it allows them to get into rapid fire / objective range quicker, gives the army an extra (objective secured) unit, and provides a bit of extra protection on the first turn.
Assault squad - do they have jump packs, or are you just taking them as a tax?
Devastators - no extra marines, which means you're losing firepower pretty much as soon as you take casualties. I would deffinitely move some bodies from one of the tactical squads, even if it means not being able to take both a special and a heavy in that
tac squad.