Is going for high speed worth it?
That's the team I currently use. The speed question comes from my pull plan - I'm thinking of getting e0 mortenax instead of welt and using token to get HuoHuo to E1, exchanging hyacine for her, this could let me reach(probably) 200 speed on Cery(183 in combat as of now, I'll have to do her E once in three turns to prolong her speed buff).
Overall - I think that the most valuable stat to go into - is her speed, since she oversaturated on crit and atk by default, don't know for sure tho.
Also don't know about the best overall team, theoretically, if I manage to get enough Robin stacks - I can reach 100% Def shred, it isn't consistent tho, cause of robin fluctuating stacks, so maybe there is other good options for teams
For insight - I usually use E on herself, I think it's only worth it to buff other characters in single target scenario(for example I made Anaxa drive Cerydra in Hoolay fight in the newest apoc)