are you sure? i couldn't interrupt the one attack that that dhrome chimera thing does in that one Relic trial at lv50. i forget the name, but it is a big attack you would normally silence.
I distinctly remember being able to, because I remember BRDs waaaaay back in the day coordinating their Blunt Arrow uses to prevent it from using its voices.

Just tested against Dhorme Chimera on 80 PLD, was able to interject Ram's Voice. Are you sure you weren't confusing The Ram's Voice with something like The Ram's Keeper?