Unfortunately there is no relation between the pool size and the luck in the direction you want. It's the opposite ...
When the luck increases - more people are joining, but then it should go down to compensate it and it look like the higher hashrate is causing the bad luck, but it is not. If no new miners join the pool a 12h block will actually take 13h

Why 'unfortunately'? Because if it was true, then a solo miner with CPU, would have much more luck and much bigger reward, then no one would need to join a pool at all.