As for Donna, she was just a vehicle for Tate's "comedy" shtick, as if confining it to her woefully unfunny sketch show of tedious catchphrases wasn't enough for the smug luvvie types at the BBC.
Hang on now, did you watch the 4th series? If you did - and you did so in something approaching an objective manner - you'd surely see how bizarre this statement is.
Firstly, Tate exhibited a much wider range of acting skills in Doctor Who than on her godawful sketch show. She is not just a comedian, she is an actor and has been in plenty of other productions, both TV and theatre.
Second, she was never just comedic relief and sure as hell never had any catchphrases. Other than the running, inconsequential joke about Donna and the Doctor being married, I'm struggling to think of any instances of straight-out comedy she was even involved in. And I've just rewatched that series from start to finish.
Third, Tate has been on various shows on BBC and C4 for years and was hardly picked because of her sketch show success or its brand of humour. Ever heard of Big Train, just to pick one of the many successful programmes she's been in that is
nothing like her show?
Fourth, what does 'smug luvvies' even mean?
It wouldn't surprise me in the least if you never gave Tate the slightest of chances to impress or grow on you as Donna. You'd hardly be the only one who couldn't look past her sketch show and, in my opinion, missed out on the best RTD-era companion. To relate to the thread's topic, to date, she is considerably more entertaining than Amy has been, and I say that as someone who likes Amy.
To be clear, I am not picking on you here. I simply disagree with your assessment of Donna Noble as companion.