Even on normal difficulty those Galleons are the equivilent of of 3rd Rates. The fluyts arent bad either...

There seems to be a big difference between 4th rates and 3rd rates both in the fire they put out and the damage they absorb. And the 5th and 6th rates are just frigates.

Basically the Galleons would be hard for you to sink and would be putting a lot of hurt on your ships with concentrated fire.

You can certainly take on one or two galleons with a group of 5th rates, demasting them and battering them into submission. But a battle is another matter.