FDMII: I can echo your experience. I had two Green System losses on the A330 and it is indeed simple to vacate at a high speed turnoff. The second event was on a Base Training detail (ie. no pax onboard ) and we tried to taxy slowly back from the runway. However, if all the fluid is lost from the steering pistons then there is no damping and at low speeds the nosewheel did not continue to castor if you get off line and we found that it tended to "snap" over in the fashion familiar to a supermarket trolley. Therefore a tow back was used.
Of interest, I once witnessed a Thai B747 land with a SYS1 HYD failure ( ie. no nosewheel steering + other faults ) Not only did he clear the runway but he taxied all the way to the stand + parked there using differential brakes. My jaw dropped!