to some extent yes, is is based on your luck.
you may open bitcoinfees.21.co and see suggested fee is for example 300 satoshi/byte and pay that amount but then see 2 or 3 blocks being mined and none of them include your transaction. simply because there is a spam attack and there are a lot more 300 s/b and more in the mempool and on top of that these 2 or 3 blocks were mined by one of those miners who fill the blocks with their own crap.
like what BitFury does with their Op_Retrun transactions which sometimes even takes half the block size.