First rule of loot: RNG is a bitch.

Percentages are percentages and there's nothing that guarantees you will EVER get a drop. If you want a guaranteed drop just get the crafted one with some myth tomes and a friend who can craft it for you.
I doubt Yoshi has a grudge against bards and has made the visor an ultra rare drop. If does, it's probably just against you for doing enrage instead of glorious Rot juggling.

Best of luck.