I absolutely LOVE Enforcers, their defense mode adds +4 shield to themselves and everyone around them, that is double than Swarm Shield and they have stagger resist on baseline. If you give them Mantra of Life that will add +2 Shields making it +6 while also giving the Enforcer a base +10 HP and a +8 Self heal if they attack. Adding Focus: Flame or Focus: Venom to that can boost +4 resist making damage reduction even greater against those weapon types. Enforcers can be literal umbrellas for damage to help others survive.
Finally enforcers are one of the very few units in the game with melee psi damage making them ignore both armor and shields on their melee attack which makes them tank busters. They are deadly in melee against things with little Psi resist.
Guild Assassins work well together with Indentured that have the Static Buildup mod. With a Breach Round active the Assassins can ignore 5 Armor and 5 Shields which is a lot. Having the Intruded troops shower the target with Static Charges and reducing the Arc resist by 2-3 can further boost the Assassins' arc sniper shot. Since Armor and Shields cannot go into negatives but resistances can. Assassins are deadly against mechanical since those come with a base -2 Arc resist. You can even use the Aeon Flux charge Tactical operation on them for another +50% damage.
The Mirage is a support vehicle it can either add evasion cover to targets under it using the same mods as the Enforcer can. But also the Mirage can apply Hallucination on enemies in an area. Hallucination is an important debuff because besides the -30% accuracy it also makes the target always flanked.Flanking attacks add +10% damage baseline but Syndicate's first mod Exploitative Targeting system add another +25% damage and accuracy on flanking.
All of these are just T4 research at max not even endgame stuff.