Depends on the class. Personally I have all block, zero dodge since I have to use my speed points for other things since I have a full versa balanced build.
When I had my tech, I had my block high, and my dodge like 1/3 of that.
When the game does a check it does so (and using the example of playboy w/ 40 block etc.):
It checks the 40 block, if that fails, then it goes to the dodge, if that's zero, then you have a high chance of getting hit if your block fails.
On the flip side: it checks 20 block, it fails, then it goes to 20 dodge and if that fails, then you get hit.
Ideally, i'd like to have 50 block, 50 dodge since if I fail the 1st one, at least I still have a high chance to not fail the 2nd check, but that's like almost impossible to do without screwing up a build.