Regarding the distortion, it was absolutely to be expected and I am surprised that you were surprised! Distortion has shown itself in recent times to be one of the easiest compromises to make in complex, compact zoom design - the fantastic Olympus 12-40 has a lot of it too - because it is one of the most easily fixed in post. Purists don't like this and they are very welcome to that view: I prefer to assess the overall quality of the finished image.
In any event, no one is going to shoot these lenses for architecture unless they are very confident with corrections in post. In fact the wide angle Rodenstock lens I use on my Alpa tech camera with IQ180 back, my preferred solution for architecture, requires lens corrections. Nearly all lenses do, if you want perfect rectilinearity. And given that fact, the only issues AFAIAC are 1) the quality of the files after the correction... and 2) how much of the FOV do you lose by making corrections.
An advantage with the A7R is that you see in the finder the 'after' FOV and that the lens seems a touch wider than advertised at each focal length so as to allow for the post corrections FOV to be about right. You don't get that on a Rodenstock.
I will by buying a Canon 24 TSE to use for architecture on the A7R. You need the right tool for the right job. But in the meantime the 24-70 with corrections can be used for most work without problems.
Regarding AF speed: to me it seems fine, and generally very accurate. It isn't as fast as the very fastest DSLRs or the Oly E-M1 but it is usually least fast enough - however, lenses with slower maximum apertures can get a bit stressed out in low light.
For me the focussing systems on the A7r are good enough and flexible enough to meet my needs very well and in fact I get a higher keeper rate than I do with a D800E, though YMMV according to your style and subject matter!