Whilst I would say that Series 7 was the lesser of his 3 series as the Doctor, I think that's a little bit harsh on Matt's overall performance and the depiction of 11, Saladfingers. Certainly in the earlier episodes like 'Asylum..', 'A Town Called Mercy' and 'Angels...' there was still enough 'meat' there for him to get his teeth into. Even 'Dinosaurs...' which had a lot of the giddy twirly stuff also allowed him to go dark, particularly once he starts interacting with Soloman. Then there was 'that' Rings of Akhaten' speech, his fear in 'Hide' and 'Name of the Doctor' was something of a gloomfest too with some powerful scenes. (I remember being impressed with parts of 'Nightmare in Silver''s performance as well, but never been in a rush to rewatch that story. I will, for Matt, sometime...probably. I'll just fast forward most of it!)
Agree with the rest of your post, though! He's magnificent in his last story. And considering the Doctor/Clara dynamic and the writing of Capaldi's Doctor, it's impossible to see the series 8 we got with Smith....maybe, with a few tweaks, 'Time Heist' and 'In the Forest....'. I mean, obviously the depiction of the Doctor would've been nothing like what we got.
As I generally liked Series 8 and really enjoyed Capaldi, particularly in the second half of the series, I'm satisfied with what we got and whilst at the time I was hoping for a fourth series with Smith, yeah, I agree in retrospect it worked out about right.