I doubt that any reputable manufacturer of a water-ballasted sailboat would spec out a trailer that couldn't handle the weight of the ballasted boat on the ramp.
The Hunter-branded trailer for my 1998 H26 is rated by the factory at 6000# GVWR, on two 3000# axles. To me, this should be more than enough to pull the ballasted boat up onto the ramp to drain without bending an axle. In my case, the axles have been replaced with 3500# axles, so even better.
Now, I know that actual boat weights are typically higher than the manufacturer claims, but you should be able to exceed the GVWR of the trailer and/or axles by a little bit on a ramp without bending them. It's not like a 3000# axle is going to bend as soon as you put 3001# on it.
If someone things their ballasted boat bent a trailer axle on the ramp, they should check the trailer and axle specs and the actual boat weight ballasted to see just how far over they were.
Not saying you should exceed the ratings on the highway, I just doubt that it was the ballasted boat on the ramp that bent an axle. Unless the trailer was significantly under-spec'd.
I did bend the rear axle of my front-drive Audi 100LS nicely, in my younger days, when I filled the trunk up with MG parts, including engine blocks, transmissions, etc., and moved to Colorado. It had a nice squatty look to it after that. And definitely wore the insides of the rear tires in a hurry.