No, you don't have to have insurance to travel. No, it is not prudent not to have insurance. Think of the worst case scenario where you will need ongoing treatment and care the rest of your life. You are a healthcare professional and you can come up with a few worst cases that could happen to anyone. There are a few agencies that have good insurance, but you get what you pay for, and with travel, you will be paying for good insurance. If you have good insurance from an agency or a perm job, you can always COBRA it for 18 months. Then rinse and repeat.
I got private insurance from BC/BS with a $5,000 deductible. You may not like that since your health cost you "thousands", but I find a $7,500 max cost out of pocket (when I include my premiums - one pre-existing) pretty comforting and affordable. In addition, I get the contracted price with visits, labs, procedures, and prescriptions. This is a large discount over paying full walk-in price. And I don't have to worry about most agency's crappy insurance.
You may find that expensive, but I think you will find good group health even more costly. Good group runs about $350 to $800 a month, albeit with much lower out of pocket than I pay. For a traveler, the primary advantage is zero after you crunch the numbers - unless you have a significant pre-existing needing group health to get a good rate without considering your past history.
It is a bit difficult to tell right now what will happen when the ACA goes into full effect in 2014. Depending on your personal health situation, you can gamble and wait until then to get coverage.