Okay, so I managed to get the best of both worlds (ie old OpenCL + driver improvements). I grabbed the AMD OpenCL drivers from the 15.12 package (which correspond to v1915.2)
Directory is: C:\AMD\Radeon-Crimson-15.12-Win10-64Bit\Packages\Drivers\Display\WT6A_INF\B297238
There are two ways to solve it:
Method 1: Download latest driver from AMD's website, extract the files, goto the NEW folders directory and replace the OpenCL dlls with the 15.12 package OpenCL dlls. Then install the driver. During installation it will give some kinda "invalid signature error" but just proceed with the installation.
Method 2: Install the latest drivers as is. Take the 15.12 package OpenCL dlls and place them in the Reality and Luxrender folder. That way luxrender will use the old OpenCL dlls to render
Why have I never come across this thread before?! I tested this (method #2) and for my latest scene, the pesky "kernel compiling" step dropped to 11 sek, from 11+ minutes! And none of the crazy RAM usage!
Incredible. Thank you! (Belated, but still..)