I've said for months that they should book Finn Balor to have the Sting mystique. They need larger than life characters, and what Balor doesn't have in size he makes up for with the "demon" persona. Part of what makes Brock Lesnar so special is that he isn't overexposed. The WWE, and wrestling in general, is overexposed, and it makes it hard for anything to feel special when you see so much of it. With Finn Balor they potentially have the best of both worlds, he's a workhorse than can be there every week, but he's also a special attraction for pay-per-view as the demon.
Another problem with the product, and the way a lot of NXT guys have been brought in, is the lack of vignettes hyping up debuts and showcasing characters. Corbin got a vignette last week (which was a good idea becuase he's weak on the mic in traditional promos) but he really should have gotten a build-up before just winning the Andre Battle Royal out of nowhere. Tyler Breeze is another guy who would have benefitted tremendously from vignettes, and with his gimmick they could have been pretty entertaining. Apollo Crews would also have benefitted from vignettes, he got a pop from a smart mark crowd but the general television audience has no idea who he is or what his character is supposed to be. He's just a wrestler that came out and had a match with no build up. This is what's killing a lot of these NXT guys and what's helping to kill the product.
If you want Balor to have the mystique of a guy like Sting, it needs to be built outside of the ring, and that means vignettes. You also need a Horsemen/NWO faction for him to go up against like Sting, which in this case you have ready made in Bullet Club. Down the line, you have Styles align with Anderson & Gallows to form a faction called Bulletproof (it's a cool name, and you don't have the rights to Bullet Club). Have Bulletproof dominate for a few months, put the Tag belts on Anderson & Gallows, and put the IC belt on AJ Styles. They need to be a credible faction. League of Nations and Wyatt Family were not credible factions. Then you have Bulletproof stalked by Finn Balor from the shadows. After matches you have the lights go out and these mysterious vignettes play on the titantron, hyping the arriving of the "demon" who will destroy Bulletproof. Keep having this happen week after week to actually build it up, then finally when Balor appears as the demon have Bulletproof sell the fucking shit out of it. "OH MY GOD, AJ STYLES LOOKS LIKE HE'S SEEN A GHOST!" The whole nine yards. Have the demon clear the ring, Bulletproof retreats up the ramp, AJ is scared shitless. Now you have a money angle, you have something that's been built up that the fans want to see. AJ Styles vs. Finn Balor at Wrestlemania. The Bullet Club leader vs. the Bullet Club founder for the Intercontinental Title. If you book that properly, with Balor chasing the belt and running through this faction, you ould have about a year's worth of programming. Eventually, you could even pull a double turn with Balor and Styles (Anderson & Gallows turn on Styles and align with Balor near the end of the feud, to kick start something new/add new life to the angle). But cross that bridge when you get there.