I really like Zhorn's suggestions from the other thread, especially the one about making it similar to BB / GFM that it is a spell that requires an attack. Then you add scaling dice to the attack roll. My only question is why not also add the same scaling dice to the damage roll since it would compete with BB / GFB?

True Strike:

Evocation cantrip

Casting Time: 1 action
Range: Weapon Range
Components: V, M (a weapon)
Duration: 1 round

You gain insights into the weaknesses of one foe and strike where its guard is down. As part of the action used to cast this spell, you must make an attack with a weapon against one creature, otherwise the spell fails.

When you roll to hit, you add an additional 1d6 to the attack roll. On a hit, the target suffers the attack's normal effects.

At Higher Levels. At 5th level, the attack deals an extra 1d6 damage to the target, and the bonus to the attack roll increases to 2d6. Both rolls increase by 1d6 at 11th level and 17th level.

Spell Lists. Sorcerer, Warlock, Wizard


I think this captures the idea of casting a spell that makes your attack more likely to hit and strike where it hurts. An arcane trickster would have to give up BB to use this, so they would sacrifice damage for chance to hit. Other martials would probably rather attack twice, even sharpshooters and great weapon masters. If this is still too strong, you can limit it to melee attacks like BB /GFB.