Be careful what you wish for, etc.
For those that want their assist based game fix you'll have to turn to anime games like Skullgirls and Arcane Heart. shaowebb can help you out.
There actually are no assists in Arcana Heart. Its cool due to the ability to equip an entire moveset of tools onto anyone and homing dash cancels with launcher combos.
Assist based fighters you can play in anime are as follows.
Nitroplus Blasterz: One character. 2 assists. Can call both assists at once. Assists are insanely powerful at times and they balance it with assists having different cooldown times. Game has a lot of cancel systems, is very fast and marvel like. Air dashes, bursts, short hops, no launchers, and a very very neat shield mechanic.
Dengeki Bunko Fighting Climax Ignition: One Character. One assist that has at least 2 different ways to summon it. Uses a stock system called Trump cards where activating one turns on a meter than drains and grants you increased combo options and stats. Activating bursts in this states extends meter. Has a 3rd character selectable that allows you to choose between one of several bonuses between rounds to adjust to folks. Air dashes, no launchers. Bursts, highly footsie based. Fairly fast and a bit more footsied.
Blade Arcus From Shining: Two character teams. No tag combos, dhc or anything. You pick one to play and one to be an assist per round. Switch if you are losing. Each partner has 3 strenghts of assist and you have 4 bars just for assists that fill. Spend for lvl1,2,or 3 assists as you see fit. Universal cancel mechanic, dashes, no real air dash, no burst but an assist based defensive assist call reversal. Highly footsie based. Combos are smaller.
Aquapazza: One Character. One Assist. Assist is always wandering around in background. No Airdash but it varies who has double jumps steps or dashes. Decent length combos. Decent footsies. Guard cancel tools and wall bounces are its main things. It utilizes an emotion system that heavily penalizes for too much defensive action and yields bonuses to offensive actions. Can get lopsided fast due to this. Basically its to force you to use a very special defensive tool over blocking. It can get hype, but matches become runaways easily as this penalty system isn't as back and forth as ones in things like UNIEL.
Vanguard Princess: One character. One assist. Assist moves around screen for setups before you call it. Assists have 4 attacks. Assists have a mechanic to nullify other assists and neutralize projectiles. Parry system. Fairly fast and footsied. Visually its got clutter like Aquapazza due to all the background stuff and assists walking around.
Skullgirls: Its mahvel baby. Your best choice for a marvel like experience overall.
I cant remember if Ougon Musou Kyoku CROSS(or Golden Fantasia Cross as its releasing as soon) has assists or is just a tag fighter. That game has some of the craziest mechanics I've ever seen so I'd be here awhile trying to recall all its boosts, burst like systems, metaworld mechanics , taunts that heal and other insanity. I dont think it was assist based though. If you like crazy though I say get it later.
TLDR: Closest choice...Skullgirls by a mile for Marvel stuff. Second best is Nitroplus Blasterz as it is the fastest and most insane by far of the choices even though its not a team fighter. DFCI is behind hit but is by far more tame and footsies. N+ has cancels out the ass, the shield system, special states and 2 assists called at the same time.