Have you tried Northern Lites snowshoes? They are lighter, have excellent floatation and I believe they may be a bit narrower and easier to walk with (though I haven't checked width against comparable MSR). I'm not sure how they compare with the MSRs for edging sharper slopes, having not tried the MSRs, but I would imagine the MSRs might be a little bit better in that regard. Looks like you get a little better edging at the expense of heavier weight and wider width.
I always wanted a heel lifter, but after reading about your experience with them closing, I'm not so sure anymore. How often does that happen, and is it a problem with new models?
You can't see them, but we're wearing Northern Lites Backcountry Recons and Elites in my avatar photo. Used them to snowshoe +12 miles around Mansfield, VT after a huge snow dump of about 2 1/2 ft. BTW, with light fluffy powder, you can still really sink breaking trail with any snowshoe, even with 30 in. decks. It can be real work.