EDIT: I have heatsinks on back of all boards in regulator area, and 120 CFM fans!
Does the backside of the regulator even get hot? I have felt the top of the chip and its very hot but I don't feel much on the backside. Wouldn't putting a small heatsink on the chip do more?
For the hashing chips those thermal vias work well as even touching the vias themselves gets hot, even better with a heatsink.
Yes, it gets quite hot. I believe they are also constructed do dissipate the heat to the board, but I did not do any research in that matter.
In my opinion the regulator heatsink is much more important than chip heatsinks.
i would guess that the regulator is half the size of a chip, but emits 3-4x the heat of a chip