Checking validation and fixing egregious errors should be considered common sense for the conscientious SEO.
I'll second that one too!
Info Architecture (old/dying SEO): - Using keywords in prominent locations. - Directory and site structure. - Valid code.
Really? You mean to tell me that the foundation of the website is old and dying? Maybe I misinterpreted what you said?
Valid Code - Old/Dying?
I would think these days it is at the top of the list. With all the technologies in place, microformats, mobile, etc, valid code is not old and dying. In fact, some technologies won't allow invalid code. Try producing a semantic outline on an invalid document, it can be very difficult.
If the bots have gotten as smart as I think they have, valid code should be first and foremost with any document - period!
Site Structure - Old/Dying?
Are you saying the Pyramid no longer applies? Isn't that about directory and site structure?