In "Start an approval" action of Flow, when we set the Approval type to "Everyone from the assined list", there is no way to track who all haven't approved their assigned approvals. We can't go to user and ask what all are pending in their screen. Also, at present we donot have any PowerShell/REST API to check if a flowrun is waiting on someone's approval for completion. When we have lot of documents pending for approvals It is frustrating to find out which documents are pending with who.
Also we need approval analytics (who approved, how long it took for approvals, Escalations etc) on the running flow instances as well as completed Flow Runs. Also we need better UI to manage all the flows that we have in a Tenant.
I believe the above are some of the very important features that flow lacks today. Flow being an amazing workflow product, Falling short of this feature leaves us no other options but to buy third party applications. After all O365 is intended to be a platform of choice for those who are looking for Productive solutions and such open un addressed areas are turning away Organizations from choosing Flow as their platform of choice for their business process automation. I suggest you to bring in these features to Flow at the earliest.