Hi, have skied Whistler a bit and there are a few odd ones on that list, Outland 80 Pro is an awesome ski and I have some but I wouldn't put them in that list for off-piste at all, more all-conditions with some off-piste capability. Based on our ski test experiences here and what our customers are telling us I would suggest from that list:
Dynastar Legend 94 (Will be the NEW Cham 97 next season, a stunning, stunning ski and can't wait for those to come in!)
Volkl Mantra - Been around a while now but still a benchmark ski for most, and very good on piste too, have blasted that one around blackcomb
Volkl Kendo - Narrower plank than the Mantra, little more flex, so not as aggressive as the Mantra. We sell a lot of these, but having skied both I would just go for the Mantras myself and back off if I wanted a chilled day I would actually go the other way to the Gotama myself if I was looking for an all-out powder ski, over the Kendo which for me feels more 50/50.
Others you may want to consider:
Scott Venture - More of an all mountain ski than just powder, but does an awesome job, especially off the back of Blackcomb in the bowls
Line Prophet 98 - A seriously under rated ski in the UK, this would be my choice for a season in Whistler. So easy to ski, smooth, REALLY holds an edge thanks to the partial sidewall it now has, and floats so well. I had a previous version in Whistler without the partial sidewall, that was awesome, but the latest Prophet is simply stunning.
So from the test data here and time on the skis, I would suggest a serious look at the Cham 97 (The 107 is even more awesome in powder!), the Line Prophet 98 or the Mantra. The Cham for me wins in powder, the Line or Mantra if you still want a ski that can do boiler plate first thing in the morning, as both have titanal layers to get those edges in.
But the Dynastar Cham series is going to get a LOT of attention next season we think! Our test videos are being edited over the next few weeks so will get them on YouTube etc as soon as I have them back. The 97 and 107 in particular were constantly in demand at the annual ski test.
Hope this helps,