In reply to BigHairyIan:
I can only offer advice for the approach from Evolene. It's a long (1600m or so ascent), but really steady walk-in to the hut from the car park - it's well marked and maintained. When we did it (9/10 Sept 2016) there was very little snow cover on the route, or the small dry glaciated areas you cross to get to the hut. But of course, that could be different now.
It's well worth looking at Google Earth - the images are now so detailed you can even see people crossing the snow above the hut!
We opted to summit and descend all the way back to the valley in one day - that's a big day out! You could of course stay in the hut for another night and have a more leisurely descent. We virtually had the mountain to ourselves as we got up & out fast and then took the more technically difficult route over the Grand Gendarme.
It's a serious mountain, a proper adventure...
There's a good little blog post on Graham Frost's site that's worth a look:
https://www.frostguiding.co.uk/blog/633/Dent_Blanche_South_Ridge.html