are you playing epic40k or epic:armageddon? (they are two different rulesets I'm afraid!)
I'm not an expert with marines, but most successful builds tend to include a couple of units of scouts, some speeders, thunderhawks, terminators, warhounds and thunderbolts
I normally run with
Tacticals -supreme commander, hunter (BTS)
scouts
speeders
Terminators (chaplain)
Terminators (chaplain)
thunderhawk
thunderhawk
Predator annihilators
Thunderbolts
Warhound
Warhound
I normally use the EUK list so you may be a few points out there (I think you could add a las razorback to the tacticals)
Generally, I try to kill small formations (blitz brigades, falcons, scouts, rangers, speeders, chosen) to reduce activation count, as well as reduce the enemy AA as much as possible, warhounds and predators are ideal for this role
The scouts and speeders can screen the BTS from early teleports and air assaults, they also make great flanking forces too, I really like the land speeder tornado for the extra range and shots over the MW version
depending on your opponent, you may want to go screaming in with the thunderhawks and terminators right off the bat (often this is the only option if your eldar opponent has nightwings....) it can often leave people reeling as they lose a couple of formations, and they can focus on the terminators and ignore your warhounds creeping forwards... I like using terminators to mash warhounds early on, but you may end up regretting being so aggressive.....
also I haven't included a spacecraft..... many successful marine players use them, the look on an opponent's face when they mass in a block, only to have your pie-plates land on them, followed by a dev formation podding in and sustaining on the shaken survivors is priceless!
I'd have a look at the epicuk.co.uk website and check out the marine armies of guys like Steve Gullick and Dave Thomas, those guys wrote the book on marine tactics and do very well with them, Matt Otter is another guy who has used some very unorthodox marine lists to great success
Hope that's been of use!
