I have had the opposite experience. It's hard for me to find healers when grouping, which really sucks. However, I have an alt Vanguard, but I haven't played him much yet. So don't despair. There are tanks out there. I guess it really just depends on your server and the planet you are on at the time.
I'm usually on the fleet. Dang, you got a nice server then. Thing is, a DPS can just respec to heals, and not need to change gear, while a DPS to tank needs a whole new set.