My average drop% of event girls is probably around 0.5%. I do on average around 400 battles with event trolls to get both girls each event, sometimes more, and sometimes less, but with 2 drops on 400 fights you could get that 0.5%.

Hard to say if thats fair or not, there where events when I got both girls in as low as 4 days, and there were events when I got second girls at last 14th day, average being somewhere around 9-10 days. With spending at least 14h a day on doing things in HH (I mean checking it once per 1-2h to use energy/collect/etc), you could argue its on borderline of being OK.