Believe it or not, this is something our team has mentioned before, as we are also heavy users of the assign plugin here on meta.
The conclusion we ended up with was something more fundamental – large topics deserve to be broken down into smaller ones for better future-proofing and traceability. Having many post assignments tends to be a symptom of hygiene for us.
With topics over 20-30 posts and assignments to various posts, readers tend to lose context themselves. Another thing I’ve seen us moving towards is that we tend to collapse all the work into a checklist on the first post, and favour topic assignments instead of post assignments.
Do be rest assured that the team will take your feedback as well.