Been researching this a lot lately. I think that Necro poison nova is the way to go in S20. Seems that the nerf to WD is substantial for group play (solo might be more powerful), not to mention the lag that they have been experiencing. With rats, ZNecro, poison nova, and possibly even poison lancer (not to mention thorns still to some degree), you have a lot of options for playing in groups. Thinking of starting with necro (one of the best season starting toons to speed to 70 and then insta-farm paragons, not to mention the one that will benefit the most from the seasonal theme), and then creating a barb for several Z variants.