Let's just put it this way. There are those of us who have farmed the Empire characters. The Emperor is the ultimate prize here. However, it will likely be faster for those who have 7 star Emperor now to field a full Empire team with Emperor at the helm than those who already have an Empire team.
Let's look at how
Emperor is already 7 star
Vader is rewarded by normal activity, if you had the rebel team to get 7 star Emperor you have a 5 or 6 star Vader.
Tarkin is in Arena. Let's say you get 2 shipments a day, that's only 33 days.
Magmatrooper is in GW, that's only 22 days.
And nearly everyone has a 7 star RG but even if they didn't, 1 refresh a day on a 16 energy node is 15 attempts a day or roughly 5 shards a day. Plus 2 hard nodes, so 7 shards a day in total. That's 47 days if you started from 0 which no one will. But whatever, we'll use 47 for arguments sake.
So that's 1.5 months. That's from starting at nothing but Vader and ending up with a full Emperor led empire team before the second run of this event. Meanwhile those who have had maxed Empire teams for a long time will be watching from the sideline.
Please be reasonable with "extremely rare" at least for the second occurrence.