I don't have a driver to share, but I have quite a bit of experience with the Hp3458a. A lot of what I've done involved writing code that ran directly on the DMM, triggering that code from LabVIEW and then downloading the data. This DMM is not like most common instruments, its old school and requires some time investment to understand.
Its true that the available driver is limited, but that's because the instrument itself is a very complex one and the task of writing a complete driver to match all the capabilities would be monumental. There are an enormous array of trigger arm and trigger event features, but only small subsets can be used together. Also the fastest sampling methods are only available if you use internal scripting and data buffers. The manual however is quite detailed and thorough about explaining these features and limitations. (Edit: The current version of the driver looks much improved, I had a previous version!)
If you want to use the instrument to its fullest capabilities you will need to RTFM, learn what features you can use to accomplish what you need to do it within the capabilities of the instrument's trigger model. After that study the BASIC programs the manual provides, see if the LabVIEW driver examples match what you need and/or how to set the features required, perhaps using the internal scripting or the right sequence of SCPI commands. Then learn to trigger the measurement, check the right status registers for measurement complete, and then learn to read back data in the format required.
If you list specifics of what you want to accomplish, show the code you tried perhaps I can be more helpful.
Craig
