With the summoning odds for a challenge event 5* at only 1.0% spread across five heroes (0.2%), it’s a no from me for additional Avalon legendaries.
Also, while I like the idea of additional Avalon 4*, I would not be in favour of it. Since it would make it harder to target a specific Avalon 4*.
I believe it is important for the f2p/c2p. It has definitely been the case for me with Jackal and Falcon from Guardians of Teltoc.
Just my 2c.