In utter darkness and All In each took me over two hours, (also supernova, the banshee mission) while no mission in HotS took me more than 3 attempts.
There may be some mitigating factors here though. First of all... I play zerg, so Obviously im very comfortable with zerg production, although its different in the HotS campaign.
Second, I'm way better at SC2 now than I was when I beat the WoL campaign 2 years ago. Yes I was diamond the whole time, but the difference between 2010 diamond and 2013 diamond is night and day.
Which campaign did you guys find more difficult?
Also the WC3 TFT campaign on hard, 10 times harder than either of them IMHO