Actually this is exactly what I'm currently experiencing. Full helltooth build, and my WD likes to just stand there and not cast WoD... half I'd say like 25% of the time he doesn't cast piranhas either... but it's especially noticeable with WoD.
Are WD's just not synergizing well with DB at the moment, or is there a setting that needs to be fixed or what? I even have TPS turned all the way up to 30 to try and see if a "smarter" bot would fix it. But nah, my guy like to just run to mobs, then randomly stop... and just stand there doing nothing while my zombie dogs and gargantuans doing all the attacking. I really don't know what changed, but even my spirit walk + Soul harvest. While the bot does seem to manage to maintain it's 5-10 stacks. It use to be quite aggressive with it. Running in and applying soul harvest to groups, refreshing the buff constantly... now, it's like I just cast spirit walk, and stay put.