Combat Medic is a base damage reduction while reviving teammates. Quick Fix (Ace) decreases deployment time of your first aid kits and applies a 2m damage reduction to anyone who uses your first aid kits. Uppers (Ace) adds a total of 10 extra first aid kits to your inventory. Your first aid kits are automatically used when down and within a 5m range of them. Inspire (Ace) allows you to revive allies 2x faster but the really useful ability to that you can revive allies from a distance (9m) once every 20sec.
A huge survivability boost, this skill tree is indispensable. Forced Friendship increases cable tie count, and tying speed on hostages. Joker (Ace) is where your survivability starts. Able to convert non-special enemies to fight for you. Converted allies do more damage and reduce the overall time to convert enemies. Partners in Crime (Ace), while having a converted enemy, it increases your movement speed, increases your health, and your converted enemy takes 99% less damage. Hostage Taker (Ace) is another huge increase to you, while having a hostage, or converted enemy, regen health every 5 seconds passively. This skill tree is amazing for group or solo games alike.
Stable Shot is a base increase to weapon stability.