Of course, if a persistent repeated sequence of such blocks were to be somehow mined back-to-back, that might slow transaction processing to a crawl*.
That is, if no other miner bothered to mine a competing block. Which, of course, is what a rational miner would do in such a situation. For then he would reap the rewards of a more-quickly validating block. (That would be the coinbase reward for solving a block).
The 'excessivity' solves itself. Through natural incentive of rational self-interest.
You keep talking about miners mining this more quickly validating block... there is no code currently that can try to validate two different blocks concurrently and pick the one that validates faster. The first one that comes in will be under validation while any other blocks come in wait before they can be validated so unless someone has a rewrite that does what you claim, the problem still exists. First block that hits will always win.