I completely bounced off of the die mechanic and wounding mechanic when I played.
It literally has a glaring in-your-face design flaw in the die mechanic.
It's literally the difference of less than a couple of percent at two target numbers. This is less than the deviation of +1 on any given D&D d20 roll. Easily fixed (if it matters that much).
Yeah, so your meta mechanic isn't there so much as a bonus to make PC's more heroic as it is to smooth out your whacked ass die and wounding mechanics...
But lots of people seem to like it anyway.
I'm not trying to convince you to give it another try (though I think you should) - I'm just addressing some of your claims. The meta-mechanic (Bennies) aren't there to smooth out the die and wound mechanics.
1) The Die mechanic stands on its own. A deviation 1.5% in very specific circumstances at most, is inconsequential in pretty much any RPG I can imagine. And I play lots of games from d20, to d6 to d100. That difference is less than most circumstantial bonuses or penalties that a GM can give on any roll. And there is a simple solution - Fudge dice.
2) The Wound mechanics exist as a direct abstraction to the fact you should be *avoiding* damage. Unlike D&D which oddly abstracts Armor as making you harder to hit, vs. absorbing damage, it splits the difference with the abstraction of HP. Savage Worlds gives characters a solid avoidance derived stat based on their skill in melee. Armor absorbs damage and goes directly to the character's Toughness rating which if an attacker can bypass that - you'll take actual damage. People are frail when it comes to life-and-death combat, as I'm sure you know. The abstraction of Savage Worlds combat is both cinematic and kinetic. If you take damage - you're *taking it squarely in the ass* - there is no HP Bullet Sponge total for being 10th level when the Thief backstabs you. Your only recourse is to Soak it, or take it. Soaking it requires a Benny. It's a hail-mary, almost a Saving Throw if you will. It's not a flaw in the mechanics. It makes combat more viceral than trading HP-meter losses like in a Streetfighter game.
3) Having said all this - there are iterations of D&D d20 that have had ALL of these features in one form or another - Fantasy Craft, Star Wars d20, and Mutants and Masterminds off the top of my head. All of which I think are some of the better renditions of d20. Too bad 5e didn't go that route.
FFG doomed themselves with their specialty dice.
They were focused on cashing in on certain IP.
They made a WHFRP and Star Wars games that had overly fiddly rules, with overly fiddly dice.
The money train ended when their licenses ended.
They still have the license. And while I highly disliked their WHFRP, I came to love their Star Wars games despite my own well documented skepticism on this forum... along with my shock at how much I ended up liking it, so much so I own the entirety of all three lines which sit solidly on my shelves next to my WEG d6 books.
The dice... yes they're a total fucking gimmick. But oddly, they clicked for my group. You can play with normal dice, it's just a pain in the ass to convert unless you get used to it. We're all professionals with lots of disposable income... we caved and bought the dice, it made for better gaming. Fuck that app.
While they still have the license (Asmodee in France) - they *say* they're going to do more content. I honestly don't care if they do more. Simply because there is no real need. They have pretty much captured the entirety of the Star Wars universe between all three lines. if they shut it down tonight, it wouldn't matter to me.
Nobody gave a fuck about their whacked ass specialty die mechanic.
The same thing will happen with legend of the 5 rings. A game that they easily could have used normal dice on. But nooooo....
Despite my extreme pleasure running their Star Wars game, I can only go so far. I fully admit the reasons why, despite me loving their Star Wars game, I never got into Lot5R is precisely because I didn't want to do the dice-gimmick. Once is enough for me. And their Star Wars stuff is pure meat-and-potatoes, no SJR fuckery, pretty damn good adventures (which is a non-thing for me since I do my own content).
But again, it's purely my opinion.