Transaction per block and block time

When we built on Stellar we noticed that getting transactions into blocks was taking a long time and created uncertainty. One way to get around it was to bid up our pushes - but we felt that would require us to maintain an entire code base around predictive pricing. Ultimately we settled on a clearing-house model to push transactions to the block.

Could someone share what the thoughts into how transactions get prioritized into blocks and how is the backlog going to be handled?