I was working on this in hopes of making a more interesting fighter to play than the current sub-classes. (and because I hate the Superiority dice)

I want to know, honestly, If it is interesting, balanced, and usable compared to the other fighter classes.  And if it isn't, please share some Ideas to make it so.

(even telling me to scrap it is useful info)

Edited: 1/19/2017 (After being away from this for a while, I reread this and made some changes, hopefully for the better. I want to try and get the technical stuff out of the way, before adding style descriptions.)

The Striker (A Fighter Subclass)

Adrenaline

At level 3 when you take the attack action you gain Adrenaline points equal to the number of attacks you hit with that turn.

The maximum adrenaline points are equal to your constitution modifier (or minimum of 1) + 1/4 your Striker level (minimum 1)

These points are used for a variety of martial techniques in battle.

You can not gain points on attacks modified by the Reactive Strikes or the Combination Strikes abilities.

Every minute outside of combat you lose 1 Adrenaline point.

Reactive Strikes

At level 3 you can modify your reactions using 2 adrenaline points. (One reactive strike per turn, maximum unless stated otherwise).

Quick: get a second attack on opportunity attacks.

Assist: If an enemy moves within 5 feet of an ally within 15 feet of you, you can use your reaction to move 10 ft. towards that enemy and attack it once with disadvantage.(if in range)

Counter: If an enemy misses an attack on you, you may use your reaction to return one attack.

Combination Strikes

At level 7 you gain these combinations which modify 2 of your attacks. 

Concussion Giver : You may use this combination in exchange for 4 adrenaline points. If only one attack hits, the targeted creature has disadvantage on the first attack on its next turn. If both attack hit, it has disadvantage on all attacks until your next turn. (damage dealt on the second hit with this combination is bludgeoning)

Sweeper: You may use this combination in exchange for 4 adrenaline points. If only one attack hits, the targeted creature loses 10 feet of movement speed. If both attacks hit, there is a contest of strength. If the target fails, it is knocked prone. (melee only)

Slice and Dice : You may use this combination in exchange for 4 adrenaline points. This combination can affect up to 4 enemies within range of the attack. The first attack that hits the target, deals damage as normal. If both hit, the second attack deals full damage to the main target, and up to 3 other creatures in the attack range must make a dexterity saving throw against the strikers second attack roll. On a fail, the creatures take half weapon damage of the striker's second attack. (melee Only)

Piercing Shots: You may use this combination in exchange for 4 adrenaline points. This combination can affect up to 2 enemies in a line behind the target. The first attack that hits the target, deals damage as normal. If both attacks hit the target, the second attack's projectile travels in a line 15 feet beyond the target. Creatures in the line beyond the target must make a dexterity saving throw against the strikers second attack roll. On a fail, the creatures take the weapon damage of the striker's second attack. On a success, the creatures take half weapon damage of the striker's second attack roll.(ranged only)(projectile cannot travel past maximum weapon range)

Mobilized Combatant

At level 10, A striker gains the ability to forfeit extra attacks during the attack action.  Each forfeited extra attack grants +10 feet of movement speed (up to a maximum of +20) this turn. Furthermore any target that you hit has disadvantage on opportunity attacks against you.

Focused Fighter

At level 15, You gain 1/5 your initiative roll in adrenaline points at the beginning of combat. (minimum 1, maximum 4) 

You also may choose to gain advantage on a single attack, with a decrease in your AC of -1 until your next turn.( must be determined before the attack roll.) You may choose to use this feature again as many times as you have attacks, each time decreasing your AC until the next turn by -1.

Advanced Technique

At level 18, you gain one of the following features of your choice.

Superior Strikes: You may add 1/2 your dexterity modifier (rounded up) to all your Strength based attacks, including Combination Strikes, and Reactive Strikes, as damage. If you already using dexterity as base damage, as you would with finesse or ranged weapons, you may instead add 1/2 your intelligence modifier (rounded up) to the damage. 

Moreover, this means that if you use a great-sword, you now use your STR modifier and 1/2 your DEX modifier (rounded up) on your damage instead of just STR.  This also means that if you are using a dagger with Dex instead of STR, you can now use your DEX modifier and 1/2 your INT modifier (rounded up) on your damage instead of just DEX.}

Superior Adrenaline: Every turn of combat, you gain 1 extra adrenaline points, and your adrenaline point maximum is increased by 2.

You may also spend up to 12 Adrenaline points during combat to improve 1 use of your second wind. For each Adrenaline point spent, you gain 1 d4 extra Hit Points from your second wind.

I really like the concept of a floating resource pool that replenishes based on how effective you are in combat. This definitely adds an interesting twist to the Fighter class, and I could also see it being adapted to other melee classes as well.

That said, definitely put some more work into cleaning up the wording of the features; have some fun with the descriptions and avoid leaving things open to interpretation. For example:

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Mobilized Combatant

At level 10, every attack during the attack action you do not use grants 10 movement speed.

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What happens if I don't attack this round? Does that mean I get a pseudo permanent movement speed bonus out of combat? It's good practice to avoid gray areas like this as much as possible by being explicit with what the feature's intended use is. 

The only other criticism I have at the moment is that the class is early game heavy with having the first two offensive features early and nothing that impactful in the late game. The Fighter class doesn't have any inherent power spikes in it other than an upgraded Action Surge and Extra Attack, so you may want to consider giving something players can look forward to in the late game stages, either by swapping around the order of the features or by hand feeding the Reactive Strikes and Combination Strikes to players (you get X strikes at Y level and gain more every Z levels). 

Thank you for your critique, and your helpful tips.  (very good points) I'll work a bit more on this and update the thread.

edit: After looking over Mobilized combat, I think that the wording is as straight forward as you can get. It works when you take the attack action. So dashing as an action wouldn't be available to use that turn.  Its like a halfway point of the two actions. 

I do understand the need to have something interesting later in the levels so that they can have something to, as you say, "look forward to in the late game stages."

I can see your point, there definitely isn't that much wiggle room to begin with, but in my experience there's always a way to clarify something further without making it too wordy. My job involves writing documentation for everything that the project teams do, so I've developed a habit of making sure instructions are as fool proof as possible. Here's how I would modify it:

Still, that raises the question of whether this can apply to flying speed, or if forfeiting a bonus action attack counts towards this.

Quote from Metezashi >>

I can see your point, there definitely isn't that much wiggle room to begin with, but in my experience there's always a way to clarify something further without making it too wordy. My job involves writing documentation for everything that the project teams do, so I've developed a habit of making sure instructions are as fool proof as possible. Here's how I would modify it:

Mobilized Combatant

At 10th level, a Striker can choose to forfeit her additional attacks in favor of bonus movement speed, up to 10 ft of movement per attack.

Still, that raises the question of whether this can apply to flying speed, or if forfeiting a bonus action attack counts towards this.

Or if you had eggs for breakfast! Wow, this rabbit hole is pretty deep isn't it...