From reading the foums it sounds like most people select a specific skill for each villager - I have been mostly NOT selecting a skill, and macking sure that most of the villagers have most skills, so there is never anyone who just does one thing. Does anyone else play like this? Am I wasting my time? Might try a different strategy on my next game

You are wasting some time. As the villagers gain skill in a particular area, they will be more proficient in it. As an example a master farmer will be able to catch crabs when he/she goes fishing, which has a higher food value. As well as the scientist gain skill they will accumulate research points at a higher pace. And of course you will need a master builder towards the end of the game to get all twelve puzzles. So these three skills, I will always set certain peeps to do the work, so that they will get the master status. As far as breeding and healing it is not such a big deal.

Help please, i've benn playing for almost 200 hours, i have just 11 puzzles but cannot find the last1, could you help me?

There is a special post for people who need Help with the puzzles! You should look there, and I'm sure you'll find what you need!

I try to have my villagers be great at one thing and adept at two more things. This is because when there is a project that needs to get done, if you change their "preferred skill" they'll keep working on that. Also you need "backup villagers" so that if, for example, your doctor gets sick, you have another doctor that can cure him or her.