I think you misunderstand the concept of "luck". Luck is a purely random/statistical thing. It does not depend on your hashpower, nor anybody's hash power.
On average, it takes X hashes to find one that meets the network target, yet sometimes, at random, you'll find one earlier or later that that average. That is luck.
However, the network target itself is dependent of the total hashpower of the network, such as that, on average, one block is found every 10 minutes. That is a deterministic process, nothing luck based.
So, if another pool increases it's hashrate, your luck (variance) is unnaffected, but your expectation value decreases.