I'm relatively new to FSA, but I highly recommend the Battle For Valhalla starter set. Even if you guys don't do too much with the Terrans, its still a pretty good deal with everything that is in there. Plus, Terrans can be uses as an ally force for the Sorylians.
The Sorylian's strength really relies on their Teir 2/3 ships. The Dindrenzi have many effective options available to them, just make sure to protect your rear.
Make sure you guys play with enough terrain, 25% board coverage is what is recommended. Playing with less will give the Dindrenzi a sharp advantage as their Kinetic Weapons will wreck anything from across the board. The Sorylians will need to make judicious use of terrain and Shunt deployment to flank and hit the Dindrenzi in the rear.
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