Fixing Martial Caster Divide

Since WotC seem uninterested in balancing out martials and casters, here is my take on it via additional martial feats that can either be used as regular feats (with the ASI) or given as free feats (without the ASI) at the specified levels.

Feat: Mob Fighter
Level 8+

ASI: You gain +1 Strength or Dexterity

You have learned how to use your martial abilities to effectively combat groups of enemies. You gain the following benefits:

Turn the Tables. You have advantage on attack rolls when the number of enemies within 5 ft of you is higher than 1 + the number of allies within 5 ft of you.

Sweeping Strike. When you take the Attack action with a melee weapon or unarmed strike, you can replace one of your attacks with an special attack which targets all hostile creatures within the your Reach.
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Feat: Brute Force
Level 6+, Strength 17+

ASI: You gain +1 Strength or Constitution

You make the most of your physical strength to overpower your enemies. 

Pummel. Your unarmed strikes can deal 1d6 bludgeoning damage instead of their normal damage, when you take the Attack Action you can use a Bonus Action to make one unarmed strike. At level 11 this increases to two unarmed strikes.

Barrelling Charge. When you take the Attack Action, you can replace all your attacks with this special attack. You move in a straight line up to your Speed, you can move through enemy spaces during this movement with no movement penalty but you must end this movement in an unoccupied space. You can make one melee weapon attack or unarmed strike against each creature through whose space you move through.
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Feat: Combat Dance
Level 8+, Dexterity 14+

ASI: You gain +1 Dexterity

You combine swift elegant movements with rapid strikes to gain advantage over your enemies.

Quick Step. If you hit the same enemy with at least two attacks on your turn, that enemy cannot make Attacks of Opportunity against you until the end of your current turn.

Jump Attack. When you take the Attack action, you can replace one of your attacks with this special attack. You jump a distance up to your Speed towards your target, you can make one attack at any point during this jump. If this attack hits, it deals an additional 2d6 damage.
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Feat: Gripping Points
Level 4+

ASI: You gain +1 Strength or Dexterity

You can thrust your weapon into the ground or wall to stabilize your balance and help you to climb.

Weapon Ladder. You can use any weapon that deals Piercing damage to pierce into a wall or similar surface in order to climb. While holding a piercing weapon in each hand you can climb any vertical surface made from stone, earth, or wood. You can use a bow or crossbow to fire arrows into the same surface to create a ladder you or others can climb.

Catching Blade. When you would be subject for forced movement you can use your Reaction to thrust a slashing or piercing melee weapon you are holding into the ground reducing the distance you are moved by half. If you are falling, you can use this reaction if you are within reach of a wall or similar surface to slow your descent, reducing the amount of falling damage you take by half.
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Feat: Combat Stance
Level 4+

ASI: You gain +1 Strength or Dexterity

You can prepare yourself for battle by shifting your weight and hefting your weapons. As an Action, you can enter one of the following Stances. This stance lasts for 1 minute or until you are grappled, restrained, fall prone, or are charmed or incapacitated.

Defensive Stance. You gain the benefits of the Dodge Action.

Guardian Stance. Attacks against allied creatures within 5 ft of you are made at disadvantage. If a creature within 5 ft of you takes damage, you can use your Reaction to take that damage instead of them. 

Offensive Stance. When you deal damage with a weapon or unarmed strike as part of the Attack Action, you deal one additional weapon die of damage.

Swift-foot Stance. Your Speed is increased by 20 ft.