1) Rusev hasn't exactly failed.
2) Snow's right. Allowing his character to build some familiarity with the audience before transitioning into a harsher, more violent character (maybe even revealing that "Adam Rose" is his stage name, but "Leo Kruger" is his real name.....probably too "inside baseball" to make any kind of difference, so too confusing, so not a good idea) and combining the good aspects of both gimmicks is probably the best way to get Rose over.
Really, though. The best thing for Adam Rose (as it is for any character in any fictional setting if you want the fans to care about them) is for him to not be a one-dimensional character. Characters that develop and change over time in response to a cohesive, thought-out story is the best idea for any of the WWE performers.
wk
As usual, you are absolutely correct and holy crap is this place different with WK around.
I saw one guy on Twitter put it perfectly: "So the whole gimmick is just the song, entrance and catchphrase. That's it?" You need more than that. A LOT more. There's nothing here that the fans can connect to, but it's easy for a mind more creative than mine to come up with so many ways to get this gimmick over... unfortunately anyone working for WWE doesn't qualify in that regard.
The NXT characters failing thing is almost hurting my enjoyment of that show. Sure, it's still fun to watch Adrian Neville vs Tyler Breeze, but you still have this thought in the back of your mind of "The minute these guys get called up to the main roster, they're dead." Like, look at the journey we've been on with Breeze. The guy's the dude who takes selfies one week, then they add his phone screen to the titantron. Then he's posing with the phone next to his fallen opponents, then he doesn't like getting hit in the face... It seemed like every week there was a new wrinkle added to the character... and then he eventually snapped after getting hit one too many times and he's become the "Vicious Tyler Breeze" who'll happily kick you in the face right back. Meanwhile, he also became a really good wrestler while he's at it, which helps a LOT. None of these things are specifically important, but you add it all together and it feels like a story's being played out.
Anyway, back on topic: Another thing that would help is WWE realizing they aren't cool. Michael Cole jumping up and down to Rose's music is the easiest way to guarantee this guy never get over.