I am st6arting a new Dual Class DM (Cause the DM dislikes himself XD) and I need help deciding on the secondary class for my character. I will be a Shark Animal Instinct Barbarian and need help deciding on which class do you think would pair better, Fighter for the overwhelming Legendary Proficiency and special strikes or Monk and go with better saves, better unarmored defenses and best of all Flurry of Bites er Flurry of Blows. On a side note I will be grappling a lot as well as to just mercilessly biting my foes!
You may want to consider using the wrestler archetype to focus on grappling and select the other dual class choice to expand your options.
Druid is almost an obvious choice to pair with an animal instinct barbarian. You can almost consider raging as a "lesser battle form" and focus the druid side on blasting.
Kineticist tends to work well with a barbarian, providing ranged/blast/utility options when not raging. The use of Con for elemental blasts and the impulses that provide armor reduce the need for investments in Dex.
Rogue (ruffian, probably) is a solid choice for skills and Dread Striker synergizes well with Raging Intimidation. If you do take rogue, you should probably consider an instinct like bear, cat, etc. that has an attack option with the agile trait (to add Sneak Attack damage) over shark and leveraging Combat Grab from the wrestler archetype for grappling. The Rip and Tear feat from Howl of the Wild is also a good option.
These are just three classes off the top of my head. I'm sure there are others (vindicator ranger, maybe?) that would work.
That GM does hate themselves if they're letting you do double martial.
If you're going to grapple a lot, I'd go monk. You can really make your saves insane as a monk along with crazy movement. I think Ki Strike works with rage too since it is
If you were playing a giant barbarian looking to do just do insane damage, I'd go fighter and get the best weapon I could.
