To promote some discussion I thought I'd show my revised proposed banlist.
Forbidden
Archlord Kristya (easy special summon lock, free 2800 beater, can't be killed, retrieves Honest? what could possibly go wrong?)I would limit it first then see what happens. One of the main issue with Agents is their boss monsters conflict with each. Sometimes Kristya is nuts, sometimes its dead in my experience.
Black Luster Solider - Envoy of the Beginning (why Konami why)I agree.
Brionac, Dragon of the Ice Barrier (I mulled this over for a while, but finally decided that I feel Brio is simply too strong a card and makes OTKs far too easy. also infinite trish loops = bad)This is fine, especially since it is extremely easy to get out and splashable in everything.
Gateway of the Six (again, I don't like infinite loops, and even ignoring the infinite loop its way too easy to get multiple searches + plays off of this thing in a single turn)Samurai is still a solid deck in my opinion, but the deck is barely doing anything right now. When it becomes a problem card, I will re-consider it.
Mind Control (broken card is broken)I agree, especially with Exceeds.
Royal Tribute (still broken even considering Dark Worlds)Banning this would probably hurt the deck beyond belief. Risky considering Dark World. The card is only really nuts turn one and can become dead later in the game when the game is simplified. 3 MST really stunts the consistency that someone can Royal Tribute. You only open up with Royal Tribute first turn with Necrovalley about only 20% of the time. How many of those games do you actually go first? 50%. That essentially means the first turn Royal Tribute happens roughly every 10 games. Wonder Wand makes it slightly more consistent, but Wonder Wand is a card which is more useful when you have board prescense which is usually after you flip Spy. Gravekeeper is still meta, but it hasn't been doing all that great in YCS.
Trap Dustshoot (I think it's been proved time and again that first turn hand control is bad for the game)I personally don't think it deserves to be banned. Mostly for the same reasons of Royal Tribute. I personally understand your concern though because of Pot of Duality, Mind Crush, and chainability is great. Being playable in every deck doesn't help it either. The information is very good, even if it is soft removal and isn't an out to monsters which are already on the board.
Limited
Grapha, Dragon God of Dark World (Dark Worlds badly need nerfs)Maybe in the future, but I wouldnt say now.
Evolkaiser Lagia (it's like solemn judgment only stronger)I think it is a little too early to say.
Leviair the Sea Dragon (powerful ability is powerful, and TG makes it way easy to get out)How many people actually run more than 1 copy? I may be wrong or be thinking of another card, but extra deck space is tight.
Master Hyperion (too strong to leave at three copies)I would probably semi limit it.
Mind Crush (powerful even without Dustshoot)This is fair.
Rescue Rabbit (need for vanillas prevents it from being broken on the level of rescue cat, but still needs to be limited)
Tribe-Infecting Virus (roughly the same level of strength as Dark Hole if not weaker, don't see why this shouldn't get a chance at retesting)I personally don't think it is very broken at all. Fabled isn't top tier right now, and theme decks have evolved to not be killed by this card. Power creep of the game made Snipe Hunter suck, so I don't think TiV would be very broken at all.
Ultimate Offering (ridiculous card, maybe even needs to be banned)I agree with it being limited. Doesn't even kill the decks it is good in.
Semi-Limited
Emergency Teleport (Psychics are dead)This is fair, but might make the psychic engine a little too splashable.
Pot of Duality (not broken but makes a lot of decks a little too consistent imo)It is a very balanced card. Consistency is good. It makes inconsistent decks live, and makes already consistent decks even more consistent. When people limit problem cards like Black Whirlwind, Pot of Duality keeps the deck alive. It is a helper card. It makes decks less flexible, but makes decks more consistent in return
Reborn Tengu (Tengu is a stupid card)This is preference, but I don't think it is as crazy as it was last format. Backrows are smaller, so Tengu doesn't have as much of an impact. Especially with 1 Pot of Avarice.
Tour Guide From the Underworld (no longer broken but instant Sangan / Leviair / Acid Golem is not cool. Nixing to two kind of forces you to run a third lv 3 fiend like dark mimic lv. 3 or something to get the best effect out of it)I agree with this.
The Gates of Dark World (again, DW needs nerfs)Not right now. I would also hit Grapha before hitting their backbone. Grapha is the problem, it is their boss. Their win condition. Gate is just the card which leads to the nutty plays. It is like Formula Synchron. Not the problem, but it is the faciliator card. The card which leads to herp/derp.
Unlimited
Dewlorean, Tiger of the Ice Barrier (assuming Brio banned) (with fishborg gone as well future fusion otks are no longer possible, no reason to keep this semi'd)Agreed.
Magical Stone Excavation (nobody really uses this anymore; two cards is a pretty hefty price)Agreed.
Primal Seed (assuming BLS banned) (useless without BLS, guess it was only limited in the first place to deter usage)Should have never been limited in the first place.