I finished all my Bloody Harvest challenges, 15/15. The only two I had to consciously work on was killing with cryo (can be more difficult with Amara Action Skills being active - and discovering that my favourite cryo weapon is fire at night), and killing Captain Haunt with an annointed terror weapon (not difficult but none of these weapons are in my regular load out). Everything else just happened - the door puzzle was opened by a teammate the first time through, and I was told how he did it in passing. All runs after that I was very careful fighting in that room so not to destroy any of the "clues".
After completing a regular mission or a slaughter run, I would follow it up with a run through Heck. Worked out to almost once a day for me (and doubling or tripling up on weekend game sessions). I did do three Heck runs last night with weremichael to finish it up.
I found the drop rates on the four new Bloody Harvest Legendaries to be less than generous. Doing all the above netted me two Ghast grenades (same ordinary variant), and one event Shotgun. The other two Bloody Harvest Legendaries were never seen.
I am impressed with this free content. I loved the boss mechanic, the simple puzzle, and the killing of ghosts to get there. While many seem to complain about everything being more difficult with ghosts flying everywhere, I do enjoy the additional challenge. I have finished TVHM on Mayhem 2. The flying ghost add just enough to keep me on my toes. And Captain Haunt is straight out of Scooby Doo. That alone was a huge win for me.
If this precursor is anything to go by, the first DLC is going to be outstanding.