Guardian seems to be the healing/tanking class. I'm playing with one now and it's awesome :D As for websites, the official beta forums should probably help ya out. They're down right now for maintenance though but just search Guild Wars 2 Beta Forums and it should pop up
Just so you know, there aren't any real healing or tanking classes. A few classes can survive better than others and a few have more healing than others, but only healing or only tanking aren't really options.
I'm not sure there will ever be a Wowhead equivalent. Wowhead worked because you would install an add on that would tract information, such as drop rates and crafting rates, and then upload to the site. Since GW2 has no add ons, stuff like drop rate won't ever be accurate, nor time efficient to collect.
A wiki will probably exist though, and would be more appropriate.