So sorry that I've not addressed your questions for such a long time. Let me attempt to do that now as objectively as I can.
The Rab Microlite Alpine is a vastly different animal. It has a W/B outer shell and weighs in at 21 oz. vs. 9 oz. here. The Flash sweater is intended as an outer layer for moderate days and should undoubtedly be layered under a W/B shell when skiing trees or when the wind is howling. Yes, the lightweight fabric will snag on tree branches when cruising by in the steeps. The combination of 850 minimum fill power down and lightweight, completely breathable fabric causes it's comfort range to be extremely versitile. From 65 degrees F to 20 F, I typically feel like I'm at room temp while wearing my Flash. Adding a waterproof/breathable layer to the outer fabric increases its durability (still risky in the trees) and it makes it warmer but will also narrow it's comfort range. Warmer temps will more readily cause overheating. I have both the Flash XR and the regular Flash. Probably if I lived in the Pacific NW, I'd wear my XR more. Here in Colorado, I don't even carry fleece in the backcountry anymore. This jacket with a lightweight Gore layer on top and 1-2 thin wool layers underneath is the most I've ever needed on our coldest -10 degree days. Hailing from Minnesota, these Colorado temps are admittedly pretty moderate.
For the record, the Flash XR is plenty water resistant for any wet weather I've encountered short of a downpour.
I've uploaded a photo of my Flash after 3 years of use. If I'd skied trees with it unprotected, it would have patches all over it. Having said that, I've not babied it either. It is either in my pack or thrown in the back of my car or stuffed into the tankbag of my motorbike whenever the temps are anticipated below 40.
Regarding its durability, as Yvon Chouinard so aptly put it: (paraphrasing) Having the best gear is no replacement for knowing how to use it.
Use this jacket wisely (not over-protectively!) and it will last a very, very long time. It will also become your most used jacket as it has become mine.