Super late to this chat, since I'm usually in an active Union Discord for Kamipro instead of HBC, but I can confirm a few numbers.

100-Ailment only has a 30% average chance of debuffs hitting. Successful Vicissitudes of Fortune increases the rate by roughly 15% (45% average)
100-Double Attack has a 40~45% average success rate. Combined with Orleans Call, becomes 60% average.
100-Recovery is as everyone confirmed, amazing, and let's you Autorun Lv100 Experts (with about 10k min-HP to tank & 2 Healers)

Atm, everyone in my union is just dog-piling the experts to complete the last 10m total Union PP. Been a busy week.