I hear you on handling your big girl in the bush. The 660 is not an Enduro machine, but I reckon it's a decent dirt road tourer. A few weeks ago I was in the bush with 2 mates on KTM 690s, tight single & twin tracks, it's been wet up here as well, it proved to be instructive.
I was on full knobs (D606s) but there was no way I could keep with the KTMs. I found the 660's handling & weight tiring, it was possible to keep up for awhile, but not for long. So much so that I did crash it (just a little bit), and badly bent the gear lever & the peg hanger (just a bit). On the KTMs the gear level is tucked right in & the pegs are attached directly to the frame, on the 660 stick out a mile on their hangers, making it much less crash-worthy.
A while ago I bit the bullet & bought a second set of wheels from ebay UK.
So the Tourances are on one set (for riding to work etc.) & the others have the knobs for snotty rides in the bush. I had a wet ride down the great dividing range (Cunningham's Gap) on the 606s & it was a bit slippery (& scary).
Having said that the Tourances are hopeless in the wet on tar, so I can't wait to wear them out to get something decent. My mate Supamanaint (he's on this forum) has tried quite a few different tyres so he'd be a good guy to talk to about your options in Australia. He won't mind you PMing him (he's got nothing else to do!!)
The other posters are right in saying you just have to persevere & get used to riding a big heavy "ADV" bike rather than an Enduro or MX bike. Where you might man-handle a 110kg MX/Enduro bike, the 660 will break your leg with it's 180kg.
I'm very lucky to have 12 acres out my back gate where we have set up a track for my boy's PW50. I've spent hours out there getting to know the handling character, throttle response etc. of the 660 on both the Tourances & the knobs.
Don't give up on your XT660, for what they are at the price, they're a good thing. If you are used to smaller bikes, they take a bit of getting used to. I'm hoping to take mine in the APC rally next year, I reckon that's it's natural habitat as well as the weekly commute.
Good luck mate.