New Class Ability -- How strong is it?

[Jack Bitters]

Doing a bit of homebrewing and cleaning up of all the classes to try and bring the power levels closer together... Had the idea for this ability:

When you make a weapon attack on your turn, rather of making an attack roll you may instead force the defender to make a saving throw or suffer the full effect of the attack on a failure. It is a Strength saving throw for strength-based attacks and a Dexterity saving throw for dexterity-based attacks. Attacks keying off of other abilities cannot be modified using this feature. Attacks turned into saving throws by this feature cannot critically hit. The DC is 8 + your proficiency bonus + your Strength or Dexterity modifier for strength-based or dexterity-based attacks, respectively

How strong is this? In my mind it allows a martial class to identify strength- or dexterity- based weaknesses of an opponent and further exploit them rather than always knocking on the AC door. Which class (or subclass) would you assign it to, and why? Or is it venturing too far from the DnD attack roll paradigm?

[Keltest]

Personally, I think its actually rather weak. A martial character isnt going to have a hard time overcoming many creatures AC just by virtue of AC not scaling as fast as to hit bonuses usually do. Whereas lots of creatures have proficiency in str saves, dex saves or both, and even ones that dont have proficiency often have bonuses equal to or superior to their natural AC. There are specific circumstances where it might result in more accuracy, but as a general rule you're worse off using this ability IMO.

Also, people like rolling dice. Giving the dice to the DM to roll would probably be a hard sell.

[Burley]

I think this is much stronger. As in, too strong.
Saves are more likely to fail than AC Attacks, so, on its face, this makes attacks more likely to deal damage. Saves are also not buffable and attacking a save renders armor and natural armor to be pointless. Likewise, class features like those of the Monk and Barbarian that add another stat to their AC would be rendered pointless. Also, Mage Armor, Shield, Barkskin, etc.: Pointless.

Plus, there are ways to force disadvantage on saves, which would be analogous to a normal attack having advantage. I'd wager there are more ways to hamper an enemy's save than to grant an ally advantage.
I think this is a bad ability. I think, if you want your fighter to be able to attack against a saving throw, give them the Sword Burst cantrip and call it a day.

[aimlessPolymath]

On average, this is beneficial against 23% of monsters published by Wizards, and provides the equivalent of approximately a +2.03 bonus to attack rolls against those monsters- a +0.47 bonus on average. As noted, it's more difficult to synergize through things like advantage- most of the time, a source of advantage will do more good than this.

Other than cheese with GWM or similar, it unfortunately just doesn't have much oomph.

Source (https://docs.google.com/spreadsheets/d/1_ZuBQ_jBbMQh1a-KQSnbhT3puQ8i84zt4inD7U6RItY/edit?usp=sharing)

[Jack Bitters]

I appreciate the feedback everyone, thank you! Interesting to see folks call it too strong and too weak. Keltest makes a good point that it may be less fun if the player has to give up their dice-rolling for an ability. Back to the drawing board, I think!

[Yakk]

What I would do is give it a twist, at the least.

Once on your turn you can do one of these maneuvers to replace an attack.

Crushing Attack
You can replace an attack with a Heavy or Bludgeoning Melee Weapon with forcing the target to make a Strength save against DC (8 + Your Strength bonus + Your Proficiency bonus). If the save fails, the target takes standard weapon damage from your weapon and is Shoved (either knocked prone or pushed 5').

Precision Disable
You can replace an attack with a Finesse or Piercing Melee Weapon with forcing the target to make a Dexterity save against DC (8 + Your Dexterity bonus + Your Proficiency bonus). If the save fails, the target takes standard weapon damage from your weapon and their speed is reduced to 0 until the start of your next turn.

Distracting Slash
You can replace an attack with a Versatile or Slashing Melee Weapon with forcing the target to make a Wisdom save against DC (8 + Your Dexterity bonus + Your Proficiency bonus). If the save fails, the target takes standard weapon damage from your weapon a creature of your choice has Advantage on their next attack on them before the end of your next turn.

Once a creature has seen you use one of these maneuvers, they have advantage on all saves against you using that maneuver for the next 24 hours.