Well, even a sword and board character benefits from the bonus attack with the shield, if the weapon has the defense property. My main point is that there shouldn't be an obviously worse choice.
i completely forgot about the defensive property attack tbh, and the cantrip can be tweaked but i don't particularly mind either way. the point of twf builds is to get more attacks anyway, whereas true strike (to me) elicits the image of a single highly precise attack. it not being great for twf builds is acceptable to me, but i would like to know what exactly you'd change.
I'm not sure. I mean, the main problem of the original cantrip is the casting time, but still gives advantage. Expertise dice can become better than that on average, you're right with that. But many cantrips at high caster level become more powerful than level 1 or level 2 spells that aren't upcasted
okay, but they don't become meta like i think your proposed true strike would for (most) martials. and typically those cantrips you mention are damaging cantrips - they are, effectively, at-will attacks meant to roughly keep up with martial attacks. i don't think these are comparable.
No reroll can be a nice ribbon feature, even if it's situational. Ignoring possible sources of disadvantage is also cool and generally quite useful. As I said, I wanted to preserve the flavor of uncanny aim to the spell, and a single expertise dice isn't enough for that.
the uncanny aim flavour is exactly why i included no forced rerolling/disadvantage - you are, essentially, completely overcoming any penalties short of full cover. having perfect aim through magical darkness without being able to see into it sounds pretty uncanny to me. that said...i can see only one expertise die on one attack (and it'd have to be either the first attack of your action or a reaction attack that can't be guaranteed to even be attempted) most of the time feeling lackluster. my first instinct would probably be to make the die scale with level - so 1d4, then 1d6 at 5th, 1d8 at 11th, 1d10 at 17th. of course, the problem there is that normally you can only ever have up to a d8 expertise die, which i don't really mind the spell breaking, but it does mean once you hit 11th level then you effectively don't need to try to get any other source of expertise dice on your attacks anymore since you can never get that 1d12 anyway. maybe a clause to specify that your expertise die with that attack can be as high as a 1d12 instead of the normal 1d8. so perhaps something like
Casting time: 1 bonus action. Duration: 1 round. Effect: Until the start of your next turn, your next attack roll gains a 1d4 expertise die, you cannot suffer disadvantage on the attack, and you cannot be forced to reroll it. Your expertise die for this attack can reach as high as a 1d12 instead of the normal 1d8. The expertise die gained from this spell increases by one step when you reach 5th level (1d6), 11th level (1d8), and 17th level (1d10).
That said, it would require a quite high level character to gain a large bonus, and would sacrifice all possible attacks for that (which means that to use it constantly, the character would have to sacrifice the bonus action every round)
i'm not particularly concerned about a high level character slamming out with a particularly high bonus on one attack each round. that's pretty good, but at the end of the day it's still just one attack, and it isn't like pathfinder 2e where that's helping you crit as well. i'm concerned about a high level character being able to easily generate expertise dice on all their attacks every round. an average of +3 (or, well, +2.5) to hit every turn on all of your attacks in exchange for a bonus action every other turn is an INSANELY good deal for, say, great weapon users or ranged characters. also, something i just realized - because of how expertise dice work, once you hit 9th level, you can essentially have your cake and eat it too, since expertise dice normally cap at 1d8. so you sacrifice 2 true strike attacks to make 1 attack at d20+prof+ability mod+1d8, then make a second attack at d20+prof+ability mod+1d4. for any build without a regular use for a bonus action, that's pretty crazy, plus that second attack matches the first at level 17.
Totally agree with you on this. It would be ok for an Adept feature, but they already have flurry of blows for that. Flurry requires ki expenditure, while a similar cantrip could go on indefinitely, surely too much. I think your previous option was probably better (i.e. scaling damage and removing synergies with Extra Attack).
yeah. unfortunate, but what can you do?
That said, the nova potential of heralds with a5e can be really nuts!
fighter/heralds are also pretty scary. just a few levels in fighter and suddenly a herald gets a second form of smite (from the brute fighter's 3rd level feature) and eventual access to 5th level maneuvers.
edit: also, i started looking through bonus action combat maneuvers on the level up site to see what sort of maneuvers could compete with our versions of true strike, and the first one that popped up was agile feint
, a second degree mirror's glint maneuver that costs two exertion to...grant advantage on your next attack. in other words, the game itself believes that a bonus action true strike should not only not be available before 4th level, but should cost class resources (unlike a cantrip). so...there's that.