Before I read any text in the post, I saw the first picture. I saw the out of focus rocks on the left side of the picture and this is what popped in my head: "busy, busy OOF areas - probably an ART lens". Then I saw what the image was shot with :-( I thought the same thing, but to a lesser extent, about the 5th image, and to an even lesser extent the 2nd image. I hated being dead-on about the lens used. It's a shame that it's a characteristic of that series of lenses.
I would also echo Johnathan Brady's remarks about the background blur qualities of the Art series.
I haven't used them I admit, but seeing their traits in that regard leaves me wanting more.
It's not the distant background, more the in between areas that could stand to transition more smoothly.
Thanks for your comments, guys!
I`m trying my best to push further just regular portraits so I`m glad to know that you see it.
As for Sigma bokeh - I`m totally OK with that. I think that it is totally subjective & also there`s a lot more things on these photographs that distract you from all that busy lines (at least I hope so.)