I finished it on thursday and yes I was in work both days, not that hard, spent the rest of the time helping others to do theirs as my kills with certain weapons help my clan mates complete theirs. It was a bit grindy to be honest that's why I haven't all three, because I can't be bothered and I haven't levelled them yet either, maybe next time I'll go for the three character completion, it the only one I have left