Mentors and coaches are often in the best position to diagnose learners.
Their assessments are useful to direct the broader program, not just for the mentor to respond themselves. Asking mentors for simple, one-minute reports after each conversation reveals the most pressing and common learner needs. The report only needs to contain a small check-list and a few open-ended suggestions to be easily actionable.
Peer coaching provides the similar insight to respond to learner needs. Peers can be taught to quickly diagnose each other, and while they won't have the same experience to anticipate and reveal problems, they have and advantage of deeper empathy of the learners' level, so can better reveal current perspectives.
A great substitution for panels at conferences are expert diagnostics, like Shark Tank, but then helpful. Instead of pitches, people jump on stage to present a challenge, which is followed by the experts teaming up to diagnose it with questions. Each session wraps up with the each expert making one short suggestion based on the group diagnostic.
With Progress Reports
When learners have their own projects, regular progress reports are a quick way to spot how you can help each individual learners best. Over time, the regular reports provide show how learners goals have evolved, or not; which struggles were solved and which were pervasive; and what the learner accomplished.
A common way of giving structure to progress reports is by dividing them into three sections plans, progress, problems (aka. PPP reports). The reports are usually done as simple emails every 2 weeks or month, with 2-3 bullet points under each of the 3 headings. At any point in time, know the best way to help each learner reveals common challenges to address.