A_D hit it pretty well, but to follow up, I currently use a shield blocking build (with NO AC) that is NOT overly specialized for it. Base blocking DR with no buffs (but hound shield) is 31 (18 ranged). I'm not invulnerable, but I'm as easy to keep up as my S&B AC tank.

In my case, with the DR build, I am wanting to get hit (piles of guard items) - so I make no attempts for AC or blur - so keep in mind that the example is not exactly equivalent to what you are thinking. The main point where I agree with A_D though is that, investing a lot of feats into this line, is of minimal value. Rather, have it as an option.

Build your guy with maxed out intimidate, but primarily focus on feats like you normally would for offense (thereby staying viable in quests where a shield basher is not needed). Then get a hound shield (by far your only option here currently). Then go to town with your blocking fun.

Also FYI, I went barbarian for the inherent DR, which is nice. However, the barbarian DR boosts are not additive with your native DR, limiting their usefulness - and sitting DR is not going to be enough to make you immune like a dex/AC build can be.

I think I did this very thing, although it has been a few months.