Only early days, and with obvious issues, but here is an analysis of the current exploration rate for the latest round.
So far (as of T68) 392 planets have been explored. This has come at a rate of 6.3 planets per tick. Over 30(ish) players this equates to 5.04 planets per player per day. This is 63% of the theoretical max of 8 expos/day/player.
Of course there are a few inactive empires. So looking only at empires that have explored (22 empires) we get a rate of 6.87 planets/day/active_empire (85.91% of max)
Tri 27 had a final exploration rate of 5.88 planets/player/day (no info on number of empires actually exploring)