RE: Dell Venue 8 Pro with Data and Charging + 4 USB Hub in use with 3 connections
Funny that you mention this, as just today I had my DV8P connected to the Dell dongle, with AC power connected to the dongle's micro port and a small, unpowered 4-port USB hub connected to the other dongle port; I then had a 128GB thumbdrive connected to the hub, as well as a portable DVD drive (that itself doesn't get enough power to run when connected directly to the DV8P via a USB OTG adapter). All ran fine (but I don't know what would happen if I also was using the other 2 ports of the hub).
One thing you might consider, to cover all contingencies: use a powered hub (and if you don't need the extra power, don't bother connecting the hub to external power).
Will be interesting to hear if others are fine, connecting more peripherals to an unpowered hub. For what it's worth, my understanding is that keyboards and mice use a smaller amount of power.