I am not a stickler for 5e rules, BUT....I did feel that constantly "helping" downed allies pulled a lot of pressure off my team and allowed me to push through a few fights.
What seems to be the case is the enemies target the lowest hp/ac targets first while sometimes targeting the closest target to them. If I have a character with low AC but then I cast mirror images or mage armor, they tend to back off them and target other characters. Also if a character is at 1 hp they hard focus them (constant down and help cycle that allows the rest of my allies to keep fighting and hope the enemy misses the next turn so I can heal the 1hp target).
Combat AI probably needs tuning to be more dynamic.
