At 20th level, a fighter with a greatsword can deal 48 points of damage every round for free (2d6 + 5 per attack, four attacks per round).
Giving up your action (your ability to deal roughly 48 damage) to absorb 45 damage seems like a balanced trade to me!
You can already move around the battle really quickly to make attacks. Lunge just lets a defender move as quickly as an attacker.You can move around the battle really quickly to intercept attacks.
Why is that?It's a good idea, but I think that the Charge feature should only be available for use if you didn't use the Lunge feature that round
I'm not even a little bit interested in protecting allies outside of combat. The point of these Fighting Styles is to increase the variety of roles a fighter can play during combatI think that the Ward should take 10 minutes of concentration to regenerate. This way, it can't be abused in battle, but is really good for defending your allies outside of combat.
The Ward is based on the Abjuration Wizard's Ward.In my personal opinion, I think the Ward should be more similar to the Monks Deflect Missile, in that you make some sort of roll to reduce damage, rather than absorbing it with a pool of hit points, but I understand where you were going with this.
These reason these features don't use a roll (like Deflect Missiles) is because they are meant to be used multiple times in the same round (absorbing several attacks, or protecting a group from one area effect). Rolling over and over and over when it isn't your turn slows down the game, and I think WotC was smart to avoid that with a simple pool of hitpoints.