I have a suggestion. It might be work but instead of deleting all groups(I know crazy) that are unrelated to bioware content in a quest to contain toxic communities why don't you work on a reorganization and isolate. This is what is known as a Kludge in software systems. A quick fix that is a temporary solution to a problem. Deleting all of your forum content will not make the problem go away. The fact of the matter is that it is not possible to predict the next topic that will be posted on the forums. What if that toxicity spills on to the other part of the forums?
I would recommend you refine your model and work on an isolation. Isolate the toxic community(in your words not mine) and then focus on developing your core non toxic features. Also I think this approach is somehow of a sweeping generalization I mean they have been constructive groups over the years. There has been a group about programming, there has been a group about Maths. If you are trying to build up a helpful community,removing features that could potentially be used for helping members of the community is a pretty bad move in my opinion. I would try and develop it instead.
I am really not buying the toxic community excuse myself cause some of it just does not make sense. This is similar to the last time when groups/polls and blogs were removed with the purpose of "enhancing user experience." However realistically this is the same experience I have received from both platforms of the software but just different layouts. Apart from the feed there is nothing here that I couldn't do on the old forums. I could even actually do more.
From my perspective, this is a thinly veiled traffic problem. I think the groups generate a lot of traffic and realistically non of that traffic has anything to do with bioware related content. I mean from your perspective why support content that does not mean anything to you right? Also if you look at the site, it does have user google analytics(I checked in the cookies) and it does not generate you any money. Keeping the website running is actually not benefiting you anything from a monetary perspective.
I personally think this website could be able to sustain itself if they had even small ad based revenue generated by impressions. This is just my guess but it is hard to give an opinion when I do not know what the infrastructure looks like.