You are correct, it is that. That's a good point. That said, I think any team would take 3 returning players with those numbers.
Final formula:
o_adj = avg_eff / opp_de
uFactor = Usage * -.144 + 13.023
altZscore = (ORtg - avg_eff) / uFactor
xORtg = avg_eff + altZscore * 10.143
if Usage > 20: adjoe = (xORtg + ((Usage - 20) * 1.25)) * o_adj
otherwise: adjoe = (xORtg +((Usage - 20) * 1.5)) * o_adj
porpag = (adjoe + (104.9 - avg_eff) - (88)) * actual_Min_per * 69.4 / 500