At a quick calc with one of the strongest and popular solo routes i got:
SO on 15 k acres with 20 mil agents 30 mil assasinss.
15k acres = 2.25 bil score
20 mil agents 30 mil assassins = roughly 2.5 tril = 5 bil score
So total score with developements and some seeds is easly over 7.5 bil
At 0 ar mod currently can be sent 5.45 tril worth of units which let's say is 100 mil poms or 50 mil poms 50 mil PA. If you saw a few BR's with this units you know what to expect.
Change around with vamps, a robo alone and other routes and see if the maximum mob attacking a solo is actually fair.
And all this considering the SO doesn't have any score into units which won't help deal damage like say 20 mil gards 10 mil traps 10 mil yobs 2 mil spikes which means an extra 1 tril worth of troops can be sent :s
So imo it's way over the overkill limit