I'm trying to work out if it's possible to report on how many activities were completed in each pipeline stage, over a specified timeframe.

For example, I want to know for all users how many activities were completed for deals in pipeline stage 1 vs stage 2 vs stage 3, over the previous week.

It doesn't look like this data is available within Pipedrive, and I've gone through the Pipedrive API docs again and it doesn't appear that there's an endpoint to state what stage a deal was in when the activity was created/marked as 'done'.

In terms of trying to track where a user is spending their time, based on monitoring the activities they're completing based on what pipeline stage the deal is in for each activity - this is definitely vital information. Especially with Pipedrive being an activity-based CRM.

I want to be able to know that if User A has completed 50 activities for the day with 80% of those for activities linked to deals in pipeline stage 1 vs User B completing 50 activities for the day with 20% of those for activities linked to deals in pipeline stage 1.

The reason this won't work to simply look up the stage the deal is in for the deal the activity is linked to, is because the deals change stage. So if this was used then it definitely wouldn't be accurate.