Speaking in general terms about diversity of the WGs, this is a challenging topic even for people who have the best of intentions. What do we mean by "diversity" and "bias" in regards to the composition of the WGs? That discussion alone could be extensive and there might not be consensus on the definitions.
If the goal in general is maximum diversity on as many factors as possible, that is a difficult goal to achieve. Given the extensive time commitment required for participation in the WGs, I think that it's reasonable to expect that a significant percentage of the members will be staff who are paid to participate because the time commitment is probably too heavy for many volunteers, and our existing volunteers already have plenty of important activities to do.
There are other ways that this phase of the strategy development process could be run that would be less burdensome for volunteers - and I personally would advocate for such an approach - but the downsides that I could foresee are that (1) the staff involved would likely also not be sufficiently diverse for the aspirations of many of us, and (2) the culture and mindset of staff can be very different from those of the volunteers, so there would almost inevitably be some loss in terms of the richness of the conversations.
What I'm trying to do here is to encourage us to have realistic expectations.
I lack the knowledge to comment on why particular individuals or groups were or weren't included in the WGs and I hope that Nicole and Kaarel can respond to the concerns that people raise here, perhaps in private communications.