The main difference between a lot of mechs in a certain videogame franchise that shall not be named is that some of them dodge out of the way of enemy attacks, while others shrug them off with sheer toughness. By giving characters two sets of defensive stats - both obligatory - and making it so that characters have to balance between both or just choose one as their main defense, we can simulate this feature.
There is a small issue with the distinction between Evasion and Armor, however, which has been bothering me a little bit due to getting in the way of speed and flow of play. It is not an issue with Evasion and Armor per se, though, I am talking about the half-rollover Accuracy-to-Penetration mechanic. Not only the math involved is not elegant, but it also adds opportunities for confusion to arise with the GM. They either need to give you the precise excess bonus or the precise rollover for you to do the rest of the math, or simply tell you to roll and then do the math themselves. By splitting the damage process like this not only does it add waiting time until you get your Damage total (or fail to deal any Damage), it makes Armor that much better than Evasion and Accuracy much better than Penetration by default.
Now this last one isn't quite entirely true, the abilities out there that serve to counter Armor are usually that much better at brutally murdering specialists than the ones that counter Evasion, and there's a few that let you add your entire excess bonus to the Penetration roll to just make them even all the time. In this way, betting with Armor is usually going to pay off better, but when it doesn't then it just plain wrecks you. In theory anyway. In practice it is easier to counter anti-Armor measures as a specialist rather than to survive anti-Evasion enemies as the equivalent. This is for multiple reasons, from the higher survivability granted by a naturally higher Threshold to... well, the fact that if you're naturally sturdy then bouncing back from a fall is easier.
Point is, I'm not entirely happy with the way using Mixed Tests as the default for mecha Offensive Actions works right now. I see a few options to fix this little issue off the top of my head.
Bunch up up Evasion and Armor into a single defense:
-With a single roll you know your Damage and there is no room for miscommunication shenanigans
-It lets people fluff their defenses however the fuck they want, alternating between dodging and tanking is what mecha do in anime after all.
-The abilities that improve your offense or defense are that much more valuable since instead of each having a niche now they always help out.
-Damage is less explosive, since Tension no longer adds 1.5 or 2 points of damage per Round but 1.
-Having a single defensive stat sacrifices a lot of in-built flavor
-We sacrifice depth of gameplay, now there's that much less room for customization offensively and defensively.
Make Evasion the only defense but turn Armor into a damage reduction stat that runs off your Genre, much like Intermission defenses work:
-It is fast. Not as fast as the first, though.
-It gives Accuracy and Penetration clearly distinct functions, with the second one being akin to traditional damage bonuses.
-I'm already considering dumping that element from Intermissions, so there would be no longer anything to mirror after that.
-I really don't want to keep encouraging people to hoard up Genre.
Mixed Tests now roll all the relevant skills die at once and only add up the excess from the two rolls if they both pass:
-Fast, though the slowest of the bunch here.
-It makes Mixed Tests work better during Intermissions as the ridiculously swingy checks they're supposed to be.
-We keep the flavor of having both defenses.
-Ideally we wouldn't have to rebalance existing abilities much afterwards, we could potentially keep them as is, too.
-We lose some depth, though nowhere as much as with the first method.
-We now have two mechanics that are exactly the same by themselves and have lost all distinctive mechanical feel they once had, which is an utterly pointless thing to have outside of a flavor perspective. We can still make counters or enhancers for each work differently to help there, but it bugs me.
That said, we could try out weirder things. We could make different mecha attacks resist using different mecha defenses, in the same way physical/mental/emotional attacks have different defenses - though they would keep a single HP bar. I'm honestly leaning more towards combining the other options, though, as that is kind of wonky in multiple ways.
Mixed Tests could use the fix, but I do think that having a single roll for standard combat stuff is the way to go. At the same time, I don't want to lose the flavor of Evasion and Armor (not entirely, at least) nor the simplicity of unified mechanics (when I start to propose fancy subsystems as fixes, please shoot me), so I'll have to think on this matter for a bit.