Inexperienced players always have trouble against all the ships. Double Hwacha is probably one of the easier things for them to deal with, as long as there is no additional piercing gun like a Gatling on them. All they have to do is go upwards or downwards, that will work with all ships against a Galleon, sometimes even when the own ship is a Galleon too. A double hwacha Galleon is in this sense an actual good enemy, since it teaches inexperienced players that when you use the 3rd axis to your advantage, death can be avoided.
A double Hwacha Galleon with a Gatling on the same side may just create a sense of helplessness as inexperienced players die, but a Gatling and a Mortar, or a Light Flak even, kill a little bit quicker, as far as my experience can tell.
What I find more devastating is the combination of Hwacha and Heavy Carronade or double Heavy Carronade, because then the ability to dodge up and down is either limited or non-existent and death will follow inevitably.