The phrase "a rather overdone" is correct and usable in written English.
It can be used to describe something that has been excessively done or exaggerated, often in a negative context.
Example: "The movie was enjoyable, but the emotional scenes felt a bit a rather overdone, making them less impactful."
Alternatives: "somewhat excessive" or "rather exaggerated".
The whole "that London" shtick is rather overdone, but there's a real deftness and lightness of touch on show as Bartlett allows Mark's story to unfold slowly and painfully, from the books by the bedside with their pages turned over, to the text messages and emails the police ignore.
"We have been rather overdone with Germans this week," his wife sighed on another such occasion.
Thus they parade around Miriam Buther's rather overdone set like angsty marionettes, which the director uses to distract us from a story that Albee wrote from the heart, complete with fractious questioning, technical finesse, and plain old talent.
A herby sausage (loukanika), sliced and fried in onions, had a rather chewy texture, like an overdone Frankfurter, but was curiously moreish.
You can try this with different objects as well - ships in bottles are the most popular form of an impossible bottle, but are rather overdone at this point.
The popular notion that the European Union is like a bicycle, which must go forward if it is not to fall over, is rather overdone.
Everyone slides between Noël Coward clippedness (I think these vowels are rather overdone for the 50s, but they're delivered cleverly) to slack-jawed slouchiness.
(Very, very slowly, to opera. Which provides nice punctuation and contrast, but is rather overdone given the general heft of the play).
It was stirring, as performances in that chapel can hardly fail to be – full of glorious sounds from the 36 voices and the instruments of the English Baroque Soloists, full of Gardiner's typically punchy rhythms and rather overdone cadential diminuendos, and the spatial effects were carefully choreographed.
