I don't really have much to say about this build. Just try it out. I might be late to the party. I haven't been on here in a while.
4x Obsidians, 1x Bounty Hunter, Gunner, and the Heavy Cannon. Add a Stealth Device to the firespray unless you want to ensure the initiative…if needed. Everything moves and shoots on 3. Form up with a tie on either side of the firespray and the other two ties together off to the side. Give them a little wiggle room. I've had and seen decent success with this build.