I’m still only beginning to get different gear sets for my warrior. I have my Tanking set and my lol-DPS set. I swap pieces around between them to make up sets for various encounters. I am aware that I should have at least 3 tanking sets, I just haven’t put the work into planning them out formally.
Tankingtips has The Fundamental Gearing Principle and Tank Like a Girl has Tanking gear sets to offer some wise advice on how to develop different gear sets. Tankspot has extensive forum posts discussing different items and gear sets. Now I just need a pack mule to haul the different sets around with me.