It all depends on the details of the whole package (truck, hitch, rack, & load).
I used to haul two bikes (Husaberg & DR200) on a hitch carrier. 500# of bike with a load center that is quite a bit farther out than you would see with a single bike - so it can be done.
The biggest problem I've had with big bikes on single bike carriers is actually getting the bike onto/off of the carrier. It's a lot of weight to manage with one person. Getting it up there isn't so bad (I usually pull up to a side hill or ledge to reduce the angle of the ramp), it's balancing it there to tie it off that becomes problematic. Small bikes aren't bad since you can lean them against the back of the truck - but the big bikes are harder to man-handle when you're solo.