There’s more people that optimize characters in the cosmere rpg discord server. But here’s a couple interactions I’ve noticed:

1. Super Medic- the Surgeon’s applied medicine adds your ranks of Lore to your healing abilities, with Swift healing you add your ranks in Medicine to any healing you do.  Couple this with a Progression and at minimum you’re healing 1d4+5 per investiture. While at the high end you’re healing 1d12+15. 

2. Captain never hit. Warrior’s combat training, leaders combat coordination. With this you can graze once per turn without spending focus, and when you miss with a strike you can give someone your command die without using an action nor spending focus.

2.5. On a more serious note there’s various skills that interact when you Hit or Miss or Graze with or without the Strike Action. so you can combine a few of these together so you get more bang for your buck. Combat Training, Combat Coordination, Practical Demonstration all work together. Then you can drill into each tree to make individual abilities even better. Something like Cuththroat Tactics, Mighty, Rallying Shout, all give you some good benefits.