Couple of thoughts....
1. Epistolary generally isn't a good use of points. You either cast the shield or the other stuff... given that you might only have 1 turn to do both, I don't find it to be woth the cost. Also, if you give him a Storm Bolter, he'll lose an attack in CC. I would leave him with the Bolt Pistol.
2. The termies could use a ride... a Land Raider would be good for them.
Also, something to consider... I think your lists will run best if you give them some focus.. ie focus on the Termies, or focus on the DC. Either is an alright choice, but I think you're list will suffer if you try to work in both (since both are pretty significant point sinks)
Hope that helps... good luck.