No matter the brilliance of a given development team, it's always more efficient to Analyze/Groom/Think about requirements before you're in the meeting where you commit to delivering those requirements.
I've been developing software with groups of fairly brilliant people for some time. The above is my genuine experience.
When a group of people encounter a set of requirements and expect to scope and commit to them in realtime while reading the document, it wastes everyone's time.
Generally, productive discussion results, yes, but that discussion is unbounded.
- One person pre-grooms the story. In times past, that's a business analyst or architect, but a member of the development team is fine. Just be sure before you go into the pitch/commitment meeting someone is warmed-up to present the story. This is analogous to an intern or resident presenting a case in a hospital to the other doctors during rounds.
- The group scopes the story in 5 minutes or less. If the 'grooming owner' has done his job breaking-down the story, then that should be enough.
- Repeat until done.
- Keep metrics on how fast you can get through everything, and if the analysis was sufficient for the sprint.