Yup, Devon is almost certainly a new character...unless he's a delusion, or someone else in disguise. It'd be really weird if he was just a random person with psychosis who was stuck with the worst mass murderers alive. We've already gotten some awesome metacommentary with "Wakanda forever" and "That's why you'll never get a movie". Looking forward to more - plus the exploration of The Republic's central question - what is justice?
I collected every issue of Priest's Justice League - I believe I got all of them with JG Jones covers, too! I thought it was really fun, though sometimes a bit flawed. Deathstroke and Red Lion were pretty great, and despite him still using Diana's gross "daughter of Zeus" origin, I really loved some of the stuff he did with her.