The problems I have with using DBH's (not to be confused with DBHR's) are:
No way to distribute aux load or loadshed power on larger installs.
No way to break out conductors used to "bring back" KP zones or triggers to the panel, short of omitting them from the RJ45, which adds more failure points or error potential for proper cable termination.
If cascading multiple hubs, you need to build your own custom cable....which in the event of troubleshooting, etc. has potential to cause further issues if cable is swapped for either an ethernet patch or ethernet crossover. Makes it very easy for a novice or even a tech not paying attention to smoke equipment.
Limits the cable that is able to be installed, or further adds to complexity if anything but solid conductors are used, adds the consideration to select appropriate RJ45's for other cable construction.
I deal with RJ45's almost daily and have easily made up thousands and I still have occasional issues, cross pinning, splits and shorts that happen. I see a lot of improperly terminated ends also. I can only imagine a DIY that has never made them or made a couple before.
We're not talking about getting ethernet to the keypads or very difficult connections that would need to be made to get a system functioning properly, IMHO adding the hub adds more labor and complexity just for the ability to click a plug in. You still need to provide a "bulk cable" jumper from the panel to the hub
If you have enough conductors installed, it's really not a big issue to install the terminating jumper at the last device and making sure additional components have at least 3 pairs to them when you're adding them. If you're worried about having to change the location of the terminating resistor jumper, just pick up a 120 ohm resistor and install it at the panel at the last pair that is the "return".
