Is buying roster space an option?
I’d probably keep 2 or even 3 Bjorn for 3* events and raid tournaments (I’ve kept two for now but will keep a third after I get around to maxing the second) - he’s superb in raid tournaments.
Nordri is great, but I’m not sure I’d keep more than 2.
One each of the others sounds about right to me.
Mireweave flatters to deceive a little bit… She’s not bad, but she’s not blown me away quite as I expected - sits in line (is: usually unused) behind Triton and the S1’s for the most part in war options.
Worth doing, but one is probably enough - maybe keep two and decide after the first one whether you want to max the other or not then.
Brynhild is excellent, but again two should be plenty - you’ll have/want Melendor from S1 maxed already, and there’s only so many healers of each colour you’ll want for wars even before you get to shift into 5* dominated teams.
Stonecleave just doesn’t interest me… I kept one incase I read of any use cases I’d missed that would make him interesting for me, but I just don’t dig him enough to level him at this point.
Depends what you have in purple already, but I doubt I’d ever keep more than one of him.