On the Brevent side there is the couloir d’ENSA. At Grand Montets there are some chutes off the top station such as the Poubelle. Pas de Chevre too. I will post some more details when I get back home. I’m not sure any of these really have the steepness and exposure of the Mallory though.
I would suggest ordering the Volopress book covering the Mont Blanc range, it is now in English:-
http://www.volopress.net/volo/spip.php?article456
Here are some sample pages
http://www.volopress.net/volo/IMG/pdf/4MBL_C3-7.pdf
http://www.volopress.net/volo/IMG/pdf/5MBL_C11-12.pdf
basically anything in the range 4.1-4.3 is steep skiing and in the range 5.1-5.6 is extreme skiing. The Mallory is graded 5.4 with an exposure of 4 (you fall… you die) so you should look for shorter couloirs in the 5.3-5.4 range with E1/2 for training laps.
This is a descent of the Mallory I saw on Youtube a few weeks ago
http://www.youtube.com/v/mSEmYkirBoE&hl
looks quite sketchy. Good luck and bring a rope.