The main clans section has been tidied up while allowing additional filters to show clan positions on a per server/realm basis. You may find this updated section by clicking on the Clans button inbetween Builds and Players.
Additionally, your clan roster page has a new "see" link under your main greater rift ranking position which now links to this new section allowing you to view clans above and below you.
A row of shortcuts has been added in your clan roster page which will show all your clans heroes ordered by class and greater rift position in your server - these stats can be further broken down for further analysis (ie. view by DPS/Power etc). This is particularly handy to see how many players in your clan are playing what class.
Remember you need at least one clan member with a hero who has achieved at least position 1000 in your server with any class for these stats to show up here.
Lastly, it may look like China suddenly shot into the top positions but in actual fact their greater rift positions were not properly factored into their clans until the 7th April when a bug was fixed. You can peruse their ranking positions to see their tier and time completion records anytime with the "see" links in their clan roster page (or browse full rankings from home page)