stormtide leviathan is a pretty solid card to throw into the deck in a more casual introductory setting, especially if you plan to focus the deck more on spells and enchantments then on creatures.
on a completely unrelated note to what you asked, but one that's still pretty relevant here, i cant recommend Shirei, Shizo's caretaker enough as a general when you want to make a budget deck to get someone into the format, not only is it a fairly strong deck, but you can build it for pennies, i run it as my main deck. While i've spent a decent bit now picking up old cards that have no shot at a reprint to optimize, my original build of the deck cost me all of $20 for the whole thing, and it was a pretty good build at that. 90% of the cards you need are commons and the rest are more or less staples(like grave pact short of a few specific cards that are crazy bombs with shirei like contamination
even though forge is expensive, id still run it, the combo with nevinyrral's disk and mycosynth lattice is really stong especially if youre going with a "mean" finisher anyways in the form of LD.
naths ability is free, and has one guaranteed activation a turn, shatter gang is pretty cool and hits everyone + can be used as much as you can sac/pay, but expensive ability activation costs holds him back a lot. personally id go with nath if youre not using the red, but red does have a lot of fun stax toys in it like goblin welder
He's likely at his most broken in artifact-heavy Arcum and Sharuum (and Sidri, I guess) builds - but they are already top tier (no one even bothers playing them in our meta) and I don't really see him tipping the scales.
I implore any of the decision-makers to test him. He's great, but doesn't seem like he should really be banned.
while i agree with pretty much everything you said, it seems pretty silly to say "he would break the game in an artifact heavy deck, but those are already top tier so it doesn't really matter" also key feature to remember (without making this thread a banlist discussion) is that the list is far from made to support competitive play, even though a good number of us enjoy edh that way, we aren't the majority and likely never will be, against other optimized decks it really isn't that bad, no, but an any joe-shome's random artifact deck in a more casual setting, he kinda breaks the game in half. making him much more unfun for a lot of people then manyyyy other cards on the banlist
i havent saw him a ton of times because of is banned status when i have but pretty much ive saw him hit early it was followed up with his mana being used to cast staff or rings+monolith, etc. to create infinite mana, and then proceeding to vomit their hand to create an absolute lockdown board-state (al la lattice, forge and disk) or won outright via drawing their deck and comboing off with something else. dont get my message wrong, hes no more broken then a lot of things that are legal in the format, and he can be down right bad late game, but his early game is one of the most explosive ive ever saw (granted ive saw him with a lot of magic Christmas land starting hands the times i've saw him, but that tends to happen when someone plays a super optimized deck)
ive saw people play him every single time that hes dropped t3 or earlier and lived to lose the sickness the person who cast him won the game pretty much on the spot, is he an auto include like some people may think, no, not at all, but any deck built to be able to abuse him can pretty much destroy at will if they get him early, his late game isnt super amazing, but his early game is so ridiculous that hes probably one of the strongest cards possible that can be played on its own prior to like t5 in a deck built to abuse it, as other mentioned roffellos does way more work late game, but he has a pretty significant period of ramp up where he can be answered, metalworker doesn't, hes out and can let you combo off t3 easy with a strong hand. is he the most broken card in the game? no, far from it, but hes a card that can win you the game pretty much instantly if you open with him
one of my most competitive decks is shirei which tends to win by being absolutely full of removal and disruption, including a fair amount of spot removal, its definitely not a suuuuuper competitive deck, but its fairly powerful and can definitely beat people planning on combing out early assuming i get the right cards as my deck has yet to be optimized due to money constraints. in my opinion running very answer heavy/staxy build has worked wonders against a lot of competitive decks ive played
gonna third Shirei, Shizo's Caretaker two already reached 3 but i think its an extremely worthwhile to consider, since it actually makes you play around your generals ability it feels way different than other decks where as you could play just about any mono black gen as reanimator instead of chainer or sheoldred
i prefer cards that wipe everything since if you want to cast something to stop more casting, someone is probably already in a pretty scary position, as mentioned awesome wincon for Kaalia, but other than that id almost always rather be playing jokulhaups there's far more cards you can combo it with to leave you in a position to win
tajic, blade of the legion is fantastic in a meta with heavy board wipe, in fact you should run some of your own, world slayer anyone? if people often dont have creatures out then use that as an way to get in with you general and some cheap haste token to buff him, a board wipe can just give you a chance to alpha strike in.
make sure you include storm cauldron and amulet of vigor not only do they give you infinite mana/landfall with patron out, but theyll both work great with the deck even when not being used as combo pieces
on a completely unrelated note to what you asked, but one that's still pretty relevant here, i cant recommend Shirei, Shizo's caretaker enough as a general when you want to make a budget deck to get someone into the format, not only is it a fairly strong deck, but you can build it for pennies, i run it as my main deck. While i've spent a decent bit now picking up old cards that have no shot at a reprint to optimize, my original build of the deck cost me all of $20 for the whole thing, and it was a pretty good build at that. 90% of the cards you need are commons and the rest are more or less staples(like grave pact short of a few specific cards that are crazy bombs with shirei like contamination
while i agree with pretty much everything you said, it seems pretty silly to say "he would break the game in an artifact heavy deck, but those are already top tier so it doesn't really matter" also key feature to remember (without making this thread a banlist discussion) is that the list is far from made to support competitive play, even though a good number of us enjoy edh that way, we aren't the majority and likely never will be, against other optimized decks it really isn't that bad, no, but an any joe-shome's random artifact deck in a more casual setting, he kinda breaks the game in half. making him much more unfun for a lot of people then manyyyy other cards on the banlist