Explanation
Let me start by saying this deck is incredibly counterblast heavy. Heavyduke is already taking two, Mist Ghost, Grandchopper, Valen, Grandfire, and Grand Gallop himself ask for one. The thing about this deck is skillfully Perfect Guarding and recycling them on top of not wasting all your damage on constant full power turns. Deciding when to burst is important.
Starting with the forerunner, Loco Battler is incredibly simple. At the same time, it's a godsend for efficiency. It takes no counterblasts or resources whatsoever, and its giving you a standard 5000 boost that can be traded for +6 on a Legioned Sin Buster and opening space for a 7 booster behind him. Or, if you really need it, panicking for an extra +3 to put any of your Strides over the edge can work just fine. Next, on the subject of triggers, I originally neglected draws (put in only 2) in favor of Kirka's utility. In my few tests though, wanting pile on Heavy Duke's skill with draw triggers is perfectly okay. This is on top of the standard eight criticals to win the game as fast as possible before you run out of counterblasts to keep up. This may be changed in favor of more Criticals in the future or trying Stands again. Grand Beat also encourages some use of Grand Gallop, letting you draw more and more, which this deck does a ridiculous amount of already.
Granguard is an absolute must for a deck without a single unflipper otherwise. Grand Rope allows you to filter Grade 3s, fuel Legion by discarding triggers, and maximize on the advantage you'll gain on top of Heavy Duke/X Rogue's draws. Mist Ghost is obvious for putting Sin Buster up at a favorable amount of power for his Legion skill or an extra +4 on your singular Strides. Chopper gives you additional burst and can also give you the much desired +8 on Sin Buster or put it on others to push, Grandsub preferred.
Mist Ghost was initially being considered to be lowered in copies due to him being undesired unless you're in Legion or you really need to push. Chopper is a little more favorable since he can be used at any moment you want him to be, but he calls for getting power on himself. I'm still working them both out at the moment, because I still like Chopper more than Mist Ghost, but Mist Ghost is a counterblast less in general, but Chopper's boosts are more general.
I'm not explaining Uru Buster.
Grandfire and Grandsub make up a lot for the Grade 2 Metalborg faults. Which is, even though Sin Buster is spearheading with insane power, the rearguards are sort of... there. Lionetter's immediate 12 swings are still nice. Bull Dump, the 10 vanilla, Russell Blizzard, and even the new one don't get enough done on their own. Grandfire, though he eats up a counterblast and has to swing at the Vanguard like Russell Blizzard, is vastly superior due to him being able to boost two of any unit for even more. Even though it needs a booster and calls for you to Stride, it's still better even if it's a tad slower. Then, we have Grandsub. Grandsub calls for you boosting him like others. However, the biggest selling point is that he's very nice about it and won't take a counterblast from you. To be even more helpful, he drops a single 4 on your Vanguard and gives it the ability to retire on hit. In tandem with Legioning to set off a Rearguard Uru Buster, Sin Buster will decimate two Rearguards and draw a card on top of them not being able to Perfect Guard him. That's fantastic.
Grandsub can work if you place Trigger effects on him as well. Don't be afraid to if you're already ahead in power from your Vanguard column. This gives you stronger swings on every other side and a retire. He's being considered to swap numbers with Grandfire solely because he's free.
With all of the Cosmic Heroes, Sin Buster has become an absolute monster, without needing a single Daikaiser. Your power ups on him are more consistent, the deck rewards you heavily for obtaining 3-5 cards per hit (5 from Duke), and his new best friend named Valen Grader searches him for you. On top of being such a swell guy, Valen also filters out Uru Busters from your soul no matter where you put him on the field. Put him on VC, he searches your deck for Sin Buster. Put him in RC? He can just blow out everything in his buddy's soul and become a big powered hero himself. Even moreso, he gives Sin Buster a +3 boost if he Superior Rode, which gets you going, and adds more if you're trying to burst.
Valen may be bumped to 3.
Grand Gallop is really good for anything you want him to do within his power. His Heart Beat can net you an additional draw for a counterblast while powering X Rogue to the number it needs. He can also give X Tiger an extra boost. Under no circumstances do you Stride Heavy Duke over him. His Generation Break rewards you with hefty advantage like others if you play power turns smoothly. That is, the ability to possibly rip another trigger. Grand Rope helps grab him and a second copy if necessary.
Finally, we have the Generation Zone. I would've liked X Falcon in here for ham, but... ugh. Anyway, Heavy Duke is ridiculous. He costs Counterblast 2, which hurts a lot. But in exchange, if you Stride him over your Legioned Vanguard, you are rewarded with five cards upon hit. Being a Glory clone makes this even simpler. Though, you're not going to want to overuse him. The second copy is to stay ahead/get back in the lead of the advantage game. The third is if you get lucky and have two open damage later on.
X Rogue is really goddamn good despite what I initially believed. He doesn't have Enigman Storm's clause, meaning your boost counts. Plus, it isn't confined to just how much you have when you swing. Triggers enable his skill too. He's your go-to Stride for being nothing but pluses for free.
Then we have X Tiger. The "Super Blizzara". I have a lot of qualms with this card compared to the Snow Element. Blizzara's boosts are flat 5000s, so you'll break a shield for each G Unit face-up. However, X Tiger takes no Counterblast from you and stacks a Critical on himself. It's... something. The deck already has an abundance of Criticals, so Blizzara still has a chance to just outdo X Tiger in power. X Tiger being more guaranteed and free is why he's here over the Cray Elemental.
Even though I was going to conclude this with the Generation Zone's explanations, I'm going to touch why I bothered adding Laurel. Despite being at 1, Metalborgs can still grab him more consistently than any other archetype in the clan. The sheer draw power will eventually get him. If you don't get him, that's fine. If you do, your game becomes utterly horrifying. Duke can swing an additional time, and for Counterblast 4 (yikes) you get TEN CARDS TOTAL. Two Triple Drives and two draws. It would take a miracle to overcome that unless you misplay very badly. X Rogue becomes a hell of a menace, and X Tiger becomes winmoar. I still hold that Laurel is bad design, but if you can find space for it, and you feel your deck can do with it due to cycling through cards like crazy, find room for it.
And... done. The deck is still working out its bugs, so there may be changes. I'm happy with the deck though, even though my problems with Metalborgs weren't entirely fixed... Cosmic Heroes are more than welcome.