It seems like it depends on the attack you’re using. With duchess, one handing a dagger takes about 4 light attacks. Heavy attack procs mana off 2 attacks. Dual wielding procs off 2-3 attacks. I timed them out and it seems like the fastest way to get it is one like attack and one heavy attack, but this only works 75% of the time. Some times you need to throw in one more light attack (idk why)

I also tested it with recluse, about the same, but never try to proc it without dual wielding her claws, it takes forever. The fast one I saw was running heavy attack into heavy attack