It's hard to say that park is "normal use" for any ski. Skis were never built to be beat on the way that park beats on skis. That doesn't mean though, that manufacturers should not do the very best to make a durable ski, but most are doing that already.
Next year's No Times have a redesigned core, using a couple different woods, keeping it light, but hopefully strengthening them.
But until some sort of new, adamantium core ski comes out that will never break ever, I think broken skis will just be a part of park skiing that we will all have to live with.