Big issue has been that important packets were filtered out by the sniffer with default settings. For instance F_UPDATE_STATE was mostly skipped, however this packet has about 30 completely different uses in the game, from triggering animation (open door, move lever, etc), updating nameplate, to operating siege UI. Packet logs that include everything are most valuable.
Another major setback has been packet logs have last byte zeroed out, so playing back packet logs recreates original game state only partially.