Are you doing Riot Blade RIGHT BEHIND the monster? Because it's labeled as a ranged attack, and I wasn't able to get the chain to activate using it at range. I never did try it up close on a monster.
Yes, I was doing Riot Blade close ranged from behind the enemy and it would trigger the Rage of Halone combo in every case. The biggest problem I had with doing this combo solo was that sometimes the Stun effect would proc on Shield Bash and other times it wouldn't.