In need of some strategic help

[Mephisto]

First of all you have to decide on what range you want to fight your enemy. If you want to engage him on maximum range, go with the seekers. At least you will hit something and not only your enemy. As you already said, go with the Battleship to keep up the distance. I would recommend not to use fighters on this range as they will only be cannon fodder for the shard cannons without support.
A friend of mine uses another approach against the RT at the moment and it seems to work ok. Use the heavy carrier, put in the minimum of fighter bays, take all the combat sensors you can get, max speed with the solar sail and everything else put into weapons (you can use the massive mount on a heavy carrier!). Set this design to point blank, you want to hit something! Keeping your distance will only get you killed against the RT. As a fighter design, use large fighters with afterburner, 3 shields and one to two weapons. Make sure the fighters are slightly faster then your carriers as the AI will first launch the fighters and then move so you fighters will have to catch up again with the carriers. You can add a combat sensor but speed is more important. These fighters will not do much damage, but they can take quite a beating and are nice target dummies.
Look at these numbers: 6 Phased Shields V (240 kt) will give you 2250 shield points plus 240 hit points, 2490 hit points in total. 8 Fighter Bays 3 (240 kt) will give you 240 hit points and 720 kt cargo. 720 cargo equals 28 large fighters. Each large fighter has 180 shields with 3 shield generators and 25 hit points, 205 hit points total. So the fighters sum up to 5740 hit points. Together with the hit points of the fighter bays you get 5980 hit points compared to 2490 hit points with shields.
You can add some kamikaze ships with organic armor to the mix and your opponent has quite a bit of hit points to wear down. Shield depleters won�t work against units and the shard cannon does not very much damage. Good luck!