Yeah, Anniversary Maria is definitely no longer a 5.5* Knight. I didn't pay close attention to Merry's abilities before the changes but once bloomed she has quite the layout now:
On top of all of that Merry now has respectable HP/ATK/DEF and her skill proc rate got a noticeable boost (used to be 21-25% at skill level 1-5) so she can make good use of that double strike chance.