in general i have a black metal shield and a black metal sword that both are upgraded to level 4 ( max ) the shield are able to block attacks. Against normal seakers this work well.
But not against the seaker soldier i often take damage no matter what.
My tactic is to run away when i see it.
- Actual there was a great tip above that say seakers soldiers cannot climp.... I did not know i just thought they where all the same ;-)

Els if there are more than one seaker then it become very dangerous.. I find in this situation that my gigantic hammer do a great job since it can knock back the seakers and damage them at the same time.. so this is an okay tactic BUT if you run out of stamina you die.
So stamina is very important. ( there are potions and food that regenerate stamina faster)
I never tried the Frostner but i can see it have some nice features such as fire, ice ect. but dont hit so hard as other things.

els another tactic that i use is to stop and listen.. if i can hear seakers walking around i choose another route around them. So take it slow and listen.
Another good tactic in the mistland is to sail around the misland and go to shore and scout and then back to your ship and so on vs walking streight though everything and back.
Just saying that often you can find building near the ocean that you rather easy can get to.
And ofcourse when you go to shore then setup a teleporter just in case you die so you can respawn near your ship and only have to run a shorter distance to get your gear back.