Question: The dominant mining pool, at the time of writing this, turns evil and uses its hash-power to reorg the chain. A customer of yours sends you a transaction. If you wait for 10 confirmations, what is the chance that the dominant mining pool successfully double-spends / reverses your transaction?
Since the dominant pool (foundrydigital.com) only has 28.4% of the network, they can't do the 50% attack, given if the second biggest pool decides to work with them they will have 49.8% of the network, so, not enough to manipulate the blocks.
But the problem with your story is the double spend part, you don't need to hold a big pool or a big mining percent to make that attack, anyone can double-spend an unconfirmed transaction. They only have to pay more fees for the new one to have a bigger priority.