
Mobile snipers receive a -20 aim penalty (snap shot), but the other additional add-ons make up for it in the heat of battle. Damn Good Ground is good for mobile snipers. Based on experience, the Gunslinger and Damn Good Ground should switch sides on the synergy chart.
Smoke Grenade, Sprinter, Field Medic, Revive, Combat Drugs, Deep Pockets, Savior. With Sprinter, Deep Pockets, and all medic synergies, "support" is what the Support does best. Supports are used strictly for medical and capture purposes. Run & Gun, Aggression, Lightning Reflexes, Rapid Fire, Bring Em’ On, Extra Conditioning, Killer Instinct. Soldiers that will either be used to take down big enemies with Rapid Fire, or walk right up and blast the last standing enemy on overwatch due to the Lightning Reflex ability. Fire Rocket, Bullet Swarm, Shredder Rocket, Heat Ammo, Danger Zone, Will to Survive, MayhemĪssaults are better suited as clean up men/women. Heavies is the one class that I build one way, and one way only. I have used all of the perks until I got a good understanding of which one could would be better suited to survive and save the world. I have learned that some builds are geared for early game battles vs. There are some optimal perks from veteran players such as myself. Some of them, such as danger zone and mayhem, also boosts rocket aoe and damage while holo targeting also affects normal attacks (personally I prefer bullet swarm since 2 attacks per round is great since you are almost always outnumbered).
However, this doesn't mean they are useless if you prefer to build a rocketeer. The heavy is another great example for this, Holo targeting, Suppression, Danger Zone, and Mayhem are all on the right side and works great when taken together. In your example with the medic, the left side of the tree focuses on healing while the right side focuses more on providing team support in the form of suppression fire, additional smoke grenades, combat drugs, etc.
Generally, there are two skills you can pick per level, and the skills on one side of the tree synergizes better with other skills on that side. There's no 'optimal' perk configuration imo since it also depends highly on your play-style and strategies. TL DR: As long as you pick skills from one side of the tree, they'll generally synergize pretty well.