Yes! I feel like rewarding older posts is very needed!

Splitting 50/50 in fact in my opinion would create the OPPOSITE effect! You're right that it might shift more curation rewards to orcas and whales, but only if they're promoting good quality content from minnows. Since minnows were getting next to nothing in post rewards, a single vote from a whale could be worth more than their last 100 posts!

If whales fail to use their steem power effectively, they will receive very little (albeit more than before) and they will suffer from lower post rewards as the post rewards will likely be split amongst many more people, rather than just the top whales!

If you're interested, here's some case studies of my algorithms !!