Wrong. So very, very wrong.
Just added it up. MNK: -60%, BRD: -54%. Both with Earth Staff. This is including all HQ Darksteel Harness for the BRD, with the better pieces of HQ Arhat's for the MNK. Both with Jelly and Defending Rings. BRD with Umbra, MNK with Black Belt.
Granted, if the MNK went HtH, he'd be 40%, if BRD went Joyeuse/Genbu's he'd be 44%, but you've also got subjob restricted Shield skill, vs. Natural A Guard. Not to mention, the Monks Higher VIT, Chakra fall back, and Dodge. I'll cancel Parry out with higher evasion and Counterattack, even though thats more favorable to the Monk. It's clear which of the two will be taking more damage. Sure, BRD has Minstrels, but you have to be dangerously low in HP for it to take effect, so one nuke(Since most of this is -Physical Damage% only, magic will still hit for majority of what it should) or powerful multihit weaponskill(Specifically Mighty Strikes Rampage/Raging Rush,) and you're done for. Since this is No SJ, I'd imagine by the time it kicks in, you'll only have between 200 and 300 HP. Someone with a good eye could also end it for the BRD before the Earring even kicks in. Permanent Damage Reduction is much more functional than latent in that kind of situation.
Not to mention, theres other jobs that could pull off further damage reduction through items/skills/ability/magic, Such as PLD or RDM. RDM can wear everything the BRD does, and throw Phalanx ontop of that. PLD, if they have Aegis, it's over.
All moot though if it's 60 cap, since the only damage reduction you'll have access to is Earth Staff, which is why I'm calling bullshit on your post since just about any SE event like the Royale is 60 cap.