Engineers are best played at the front lines. Handout kevlar to who needs it, buff guns, set up turrets as backup fire, and between spawn waves push forward and set up mines in key areas to thin out attackers. To go beijdenemy lines is selfish and “lone wolfing” it, you hand out the two best buffs in the game…stay with your squad.
Heavy medic is best medic. Insane amount of supplies, and careful use of the auto run when you buff someone negates your movement penalty as you bounce between teammates. Your higher health makes you a sturdier target that helps your team stay alive longer. Just rememer to duck and heal yourself when needed bcause they WILL be trying to kill you!
Soldier, chokepoint buster. Works well with all types but I prefer medium for the extra supplies over a light because im always tossing munitions. I can see the light advantage for a flank+ molotov.
Operative is the only “behind enemy lines” guy. Always be a light unless you have a master plan, cause you need to bust out when things go bad. Honestly, disguising, waiting foe the enemy to all push up, then hacking ALL their turrets at their backs can raise some serious hell. Your goal is harassment, confusion, and recon. Also, caltrops are THE best defensive tool. I shouldn’t have to explain why.