This is an older question, but, the topic is an on-going one on BP hunting forums, so, here is my two-bits worth.
I always carry a bivy when anywhere away from my vehicle and a light siltarp with it. I have three different I.D. bivies and have had several others, I.D. makes the best bivies I know of, by far.
These are for EMERGENCY camps and not really designed for lonef term camping. Mine are the yellow eVent Bugaboo plus yellow Silshelter, for winter hiking, green eVent South Col plus green I.D. poncho for early season o-nights if caught too far from my truck and my original Unishelter plus Moss Wing tarp or another Siltarp for whatever, I seldom use this now.
My favourite rig for about any shortterm hunting is my I.D. Mega Sola in O.D. plus an I.D. Silwing in O.D., fast and easy to set up and bombproof, but, not the lightest combo out there. This will handle any weather that I will even think about going out it and is my usual choice for hunting.
For trips longer than o-nite or MAYBE two nights in moderate rain or really crappy B.C.-Alaskan type weather, I go with my Hilleberg tents and a light tarp and will use my Kifaru 8-man tipi with stove whenever I can get it to where I will be hunting. For ONE combo that will do it all in harsh weather, a Hilleberg Jannu tent plus an I.D. eVent Unishelter and Siltarp II or III is the best available option I know of; this is pricey gear, but, well worth it for use in vile conditions and longterm situations.