I have a Kubota 3 point hoe with the subframe, etc., on my L3010. I used to have a Case loader backhoe as well. Needless to say, there is a big difference! Nonetheless, I have had no frame related troubles, etc., with my hoe. I assume the Kubota engineers know what they are doing and match the stresses, etc., to the actual tractor and subframe (or vice versa), so I would not expect any such issues. A more generic hoe on the same tractor may cause problems, however, because it may not have been as well matched.
Now, a hoe is a very useful attachement. Beats the heck out of a pick and shovel!
Still its clearly a lighter duty piece of kit. If I were using it professionally, I would probably find it inadequate. Then again, I wouldn't suggest using an ag tractor for excavating if I were doing that for a living. I could do stuff with my Case that I couldn't dream of with my 3010 and backhoe - including leaving 4" grooves in my lawn ...