I like how you try to adhere to the Ultramarine markings, that detail adds alot!
I would suggest for your whites you apply either a light brown (for a more "warm" look, leaning toward a "cream", I would suggest this) or a grey (a more cool look, I tend to use that for more modern or new looking things) before the high end titanium white: it is too easy for it to look uneven or "chalky".
It will also act as a border between the neighboring colours and the white.
I think you did a great job centering your drilling of the gun barrels.
Very good to see the lines on the purity seal parchment, maybe squiggle them a tiny bit more or add the occasional break with each of those lines to better look like text?
Maybe a tiny bit more brown shade paint on that gold to define the details a wee bit more?
Flesh tones could use a bit of shade as well since they are very smooth and uniform which is what you want as an initial coat.
You have really good instincts on where to edge highlight, try to keep the "light-source" consistent with your lens white dot with the direction of the strongest edge highlights.
I have been trying to perfect hazard stripes, the one on the terminator is nice and sharp, I would suggest just like how you added the brighter yellow as a border highlight, you add a very dark grey on the black in the same way... it will look awesome.
Both tabbards and the helmet "frill" (Crista) Could stand a wash or shade applied, to smooth out the colour transitions on the cloth and to fill any bright white that snuck into the cracks and crevices within the strands.
The work you do on your bases look very well done and your painting is very accurate, that is 90% of the work of painting well.
This is pretty much a list of everything that jumped out at me looking at the pictures.
It all comes down to when you say "good enough".