I can confirm that their customer service is fantastic. I had to hold maybe 15 minutes this time before I spoke to someone but they have always been very helpful and solved every issue I have had. Having said that after confirming the withdrawal address and proceeding with another withdrawal, it still hasn't shown up on the blockchain and over the years every transaction I've made always appeared immediately even though it may have taken taken a while to confirm. I will call them back if it doesn't confirm.
Just to be sure, you doubled check it's the correct address, right?—by double checking, I mean not just the first few or last characters.
If so, it could just be a slight delay. I've experienced this in other CEx, though I did not wait more than 30 minutes. Or as a fellow member above mentioned, kraken could be doing additional checks before they process your transaction. And yes, once kraken has processed/broadcasted your withdrawal, it should immediately reflect in the blockchain.