I like this list, seems pretty solid. My recommendations would be to swap the drop pod on the tac squad to a rhino, unless you want to have them deep strike first and hold back the Sternguard. I would recommend taking all of one kind of Combi-weapon, like all melta or all plasma. It's a small percentage that a plasma will cook it's user, so all plasma is definitely not a bad choice either, the trade off being, you already have ap 3 rounds with special issue ammunition. So what is your goal with the Sternguard? Having the Dev's run the anti-tank game and then using the combi-plas to be termi equivalent killers is an idea.
Also, I personally like to run my Tactical squads light on special weapons so I can either get more space marines, or get more elite stuff. You could drop all the special weapons on the squads, including sergeant weapons, and instead take a rocket launcher each. You could have the points for an extra squad or a dreadnought in a drop pod.
For the Dev's, I'd keep them as is. They're cheaper than lascannons at lascannon stength against Tanks. And they also double as being great anti infantry, firing the frag missiles.