Those drag-and-drop are single aspect commands.
If you've given the henchmen a command to GOTO a certain point ... clicking that "All Defensive" button won't make them start following you, they'll still be on that GOTO positional aspect.
I could run in, slap an Aid Other on a pet, then run back ... something like TWICE, for every one use of Repair. At least.
Repair as it stands is the next thing to useless.
The mission scales improperly, that's why.
A Lieutenant is +1 to you, even at even level. So a Lieutenant who is one level higher than you, cons as Orange, a.k.a. "+2 to me".
Proton is probably the number-crunching "nerd" stereotype. and Twinshot's likely the "social butterfly"/"Popular Girl" who knows everyone, everywhere, and is just SO very amazingly cool. 😄
This would still require a great deal of intense work.
Because, you see, there isn't anything on the other side of the War Walls. Not even empty land. Just a fairly basic skybox. To make it work like the boundaries in, say, a Mayhem mission (those blue force-fields you mentioned), the dev team would have to actually model something for you to see, on the other side of the force-field.
The answer to the OP's question is:
A TOTAL GROUND-UP REWRITE OF THE ENTIRE GAME. Every line of code. No exceptions.
Welcome to City of Heroes II ...!
Seriously, that's what it would take.