I mentioned a long time ago that DT3 was going to have a group that all supported one another and mentioned a key unit in the group. That one being specifically a support unit that could heal/shield allies. This is no longer happening, but... it is happening. Instead I've repurposed that idea to be a bit more broad. In the later parts of the game, the protagonists are constantly facing off against a certain group, and within this group are various support units. Instead of having a single enemy type that can do everything and only support its squad, it can now support any ally within its faction. (Remember in the scan info, the icon that showed if it was a Mario or Zelda related enemy?)
Before this change, I was going to allow support bots to use their abilities on one another. With this more broad approach, I felt that would be a bad idea, and for science I tested it. It was rather disheartening to see a shielding bot being fully recovered by a healer when it was nearly down. Even worse though, was the healer being shielded. This constraint felt right after that.
The healers and shielders can only target a single unit at a time. Healers check all nearby units and prioritize both on the group's current HP% and a hidden value that all of that faction's enemies have. (Some of them are a hair bit more important than others.) At the time of typing this, they can heal up to 150HP/sec, but after doing more field tests, that may change. It tends to keep its target between it and the player, but it still has to be close to its target to heal.
The shielding bots can shield a single ally and make it completely invulnerable. It has no cooldown or overheat, so it's able to hold the shield indefiniately, however it has to be fairly close to its target to shield it. It isn't as active at playing 'keep-away' from the player as the healer.
There is one other type of support unit, but that one is a secret.
All support units have an auto-regeneration that (once again at the time of typing this) recover 15HP/sec.