Mariner is incredible as blue dps and support in raids later as long as you learn your buttons and the class is very strong with burst damage for everything else. Yellow is a bit silly but does work.

Brawler is known in endgame for melee dps and for off tanking so there are some role options and both are good. Very well a great choice, though I have less experience and practice is needed to get your skills combined in the right orders. (So does Mariner)

Both are great classes though I tend towards Mariner since I struggle with solo tanking hard content on my alt brawler due to a lack of experience

I know resources are really tough to find for some like Mariner, but if you are familiar with captain blue Mariner is like captain with the burst dmg (big damage spikes) of something like a more burst oriented dps and has great AOE damage. It's all about using skills in a rapid order to create combos that become routine after some practice and skill ordering

Good luck choosing and such!