Our group came up with a strategy for this map which has proven successful consistently. Here's a video recording of one of our runs to show how to clear Wheat and Chaff on cataclysm easily and effectively.

Summary:
A scripted large wave starts the second you step into the trigger area, sit it out in the area shown in the video and the ogre comes immediately after. Deal with it in the open area beside the wagon and a tight team should have no problem defending while moving the sacks after.

The common mistake is to rush to the sacks and the team will have to deal with the initial wave on top of non-stop rats and stormvermins plus an Ogre.

Hence this strategy basically turns the sack collection into easy mode.


Feel free to check out our group Warhammer Vermintide SG: http://steamproxy.net/groups/WHVSG
We consist primarily of players from Asia, and we help each other complete legit Cataclysm runs.