DITA 2.0 planning: What deprecated elements need to be removed?

Also, are there elements like <topicsetref> that do not add value/are duplicates and should be removed?
Or little used features or functionality that do not add sufficient value and should be considered for removal?

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Best, Kris Kristen James Eberlein Chair, OASIS DITA Technical Committee Principal consultant, Eberlein Consulting www.eberleinconsulting.com +1 919 682-2290; kriseberlein (skype)