I finally have the strength to post this reply...
Yeah, Martial Mastery seems like something that basically shouldn't be used in certain matchups. Quince is one of those matchups, as Quince really wants to dodge to set up his washing machine vortex (often/usually, but, of course, not always), and Grave's 7 throw beats all throws & blodges that Quince has. Theoretically, it's also important to keep 7 & 8 throws in hand to defend against Quince's K spin, but I feel like the Grave can occasionally go HAM and defeat Quince after throwing all of his 7s & 8s in the garbage. If Grave can get far enough ahead, and attack often enough into the K spin, maybe the Quince can't finish things even if he starts up the washer!
One thing that is scary, though, is Patriot Mirror. If the Grave player is going TOO HAM with 7 throw, then a dodge/7 throw Patriot Mirror turn could turn into a loss of some kind!
Also, ah, I don't feel like the 'Look at the opponent's hand' peeking clause of Martial Mastery does much against Quince. He's going to show ye a lot of his Face Cards, either through Two Truths or his innate, and a lot of his Aces are going to be known info as well. Ye aren't getting much value out of this part of the ability, I'd say. Maybe ye spy a seven throw and force a dodge during a Patriot Mirror turn or something down the road because of it, but it's less good than it looks, in my opinion. There's also the potential of seeing a Quince with three 2s in hand & intentionally not countering Two Truths if the Grave only has one counter - because the Quince is likely going to get his Truth on nevertheless, and it's possible that Grave's attack is more valuable than denying Quince a few cards. Using one against a KD Quince is still usually wise, as Quince's defensive options are fairly limited & sometimes he can't guess a certain way.
In addition, for people who are familiar with MTG, the 'Then discard a card' part of Martial Mastery is like looting. It does draw 2, but it's more of a filtration tool than a draw engine! It doesn't even put ye up a card! :0 Ye are discarding the 7 for the ability, and then something else, which evens out drawing two. It's minimal "value" - viewed this way!
One other thing about Two Truths is: Pay attention to the cards in the piles! When the Quince puts a 2 and another card in a pile, and three cards in the other pile, generally give the Quince the three cards! I don't know about other Quinces, but I view the 2 as the most valuable thing to reveal in the abstract off of a Two Truths besides a Joker! Deny the Quince more selection - do not give him a 2 and another card if ye can help it! Constrict his hand as much as ye can!
Ooh, and one Grave vs. Gloria thing I think that ye were overvaluing was countering Healing Sphere! Once Gloria has a Sphere attached, she breaks even when she Healing Touches back a Hearts (Let's do the math: Discarding two cards to recur one Hearts. Net hand size -1. And then the card from Healing Sphere pushes her back to 0.) Once she has a second Sphere attached she is +1 on cards in hand every time she's able to heal. Here's how ye want to answer this: By knocking her down! Countering the second Sphere slows her down a little if she's trying to go for the checkmate situations that I'm generally looking for when I play her, but ye aren't setting her back - she is setting ye back!
Grave spends one more card than Gloria in attempting to fight her on this axis, and he draws far fewer cards than a Gloria with her engine going! Arg's counter costs a card, but gives Gloria back her card (unless Jack is being countered - more on this later!), and it allows the Gloria to potentially reshuffle the 10s back into her deck & re-draw them over the longer game that Arg typically plays. Persephone's counter is mainly for being cute when ye have them under ye control, but I guess it could make Gloria pay life sometimes that throws off the math in Perse's favor. For the most part, though, I doubt it.
The thing that ye actually want to counter, as was stated previously stated somewhere else (maybe in this thread, actually?), is the Jack ability, Bathed in Moonlight, because... From my point of view... Let's say that ye tried to win combat with a throw and the Gloria plays Fast J, which is a 2.2 speed attack - a fairly decent-to-good speed in most matchups. Well, the Gloria wins combat, can potentially combo into a straight for some solid damage, and then can buy back her Jack at the low cost of it retroactively dealing 1 damage to the opponent instead of 5 and also healing her for 4! What if it's a blodge? Throw into J works, too?! This move is absurd! :0 Counter Bathed in Moonlight whenever ye can, in my opinion, especially on the non-Hearts Jacks, since they can't be recurred! Extra-especially with , because Gloria's Jack will go into the discard instead of the bottom of the deck - because the Jack ability isn't played from hand!! :0
Anyway, yeah, I'm sure that @MR75 knew all of that already, but I wanted to explain a bit about how I was looking at the matchup from the & point of view!