Been back and forth with SideFX several times already on this ( your support never replied to me…) and the conclusion was that this is probably an issue with Deadline as SideFX couldn’t reproduce it in HQueue or running the command manually.
Houdini tasks are cooking parts of the network which should not be cooked when the scene file is loaded (hou.hipfile.load() called in hrender_dl.py). This includes OBJ nodes which have their Display Flag off and no dependents, and DOPnets which are not referenced or required by the ROP submitted to Deadline.
This is particularly bad if a scene is submitted when the timeline is not set to frame 1. In this case it seems any Dopnets in a scene are run to e.g frame 100 even though there is a cache loaded further down the network tree. This leads to hipfile load times of 10 or 20 minutes instead of 10-20 seconds.
I’ve worked around it by modifying the submitter to force the timeline back to $FSTART. But there is clearly something odd going on.