Hm Maybe, cause I play the dualist on Friday.
No didnt try that, But normaly It should work like this?:
Legionnaire, Keeper, Archer, ZITHER!, Isabela, or Skywatcher and get 10 level doest matter 1-10 or 7-17 right?
And for each Char 1 Star.
the challenge always starts friday (in Austra it would start around 6 or 7 pm)
here is the challenge description: This weekend only: Earn 2 (= first star), 4 (2nd star), ..., 10 (fifth star) levels while playing as the Legionnaire, Keeper, Archer, Virtuoso, Duelist, OR Avvar.
so you can earn all the (10) levels playing just the Archer or whatever other mentioned character and not as you stated 1 star for each char.