I'm trying to come up with the best possible Multiple Man deck for every character in the game. I really like playing characters solo so I can learn them. While the decks obviously change some things, general skill and knowledge with the H&H character carry over. It's especially nice for learning an anchor characters.
Some of my decks:
Sentinel:
Fou-lu (Main)
Multiple Man
Megaman X
Megaman X lets Sentinel apply really strong pressure and perform quick cross-up j.S during flight. Fou-lu gives him 3 X-Factors so that any Hyper Sentinel Force or Hard Drive catch is a dead character. I also thought about Ultron for faster flight movement or one of the special-cancel moves to let Sentinel Force -> Flight happen, but I don't think either of these would be quite as helpful as the two cards I picked out.
Dr. Strange:
Lilith (Main)
Multiple Man
Kingpin
Lilith + Kingpin lets Dr. Strange take 80-90% of an opponent's bar with every Spell of Vishanti, allowing him to always have the threat available. This is also a good counter to Fin Fang Foom decks. Spell of Vishanti hits for about 450K with this setup. Assists will take about 800K, and you will steal 3-4 bars if you happen to hit an assist and a point character together.
Dante:
Mephisto (Main)
Multiple Man
Serpent/Daredevil
Dante is already one of the safest characters in the game, but the ability to cancel specials into each other gives him really nice solo setups, including aerial cross-ups. Havoc Missiles into Air Trick now works anywhere. The consistent meter gain allows for an endless offense as well as the ability to retain meter gain during Devil Trigger, which gives Dante an invincible approach option from which he can cancel into Hammer.
Firebrand:
Ultron (Main)
Multiple Man
Fin Fang Foom
Pretty much nothing in this game beats a super armored Bon Voyage. You're not going to get much use out of Firebrand's level 3 thanks to Ultron burning up meter, and X-Factor provides about the same bonuses as Luminous Body. So, you're basically trading Dark Fire for permanent X-Factor, and I think it's a good trade. Firebrand needs to go for a reset after Dark Fire anyway since his damage is so low. Sometimes you'll only start the match with 2 bars and will have to work up to 3 for the X-Factor, but it's generally not a problem since your offense is nigh unstoppable.
Super-Skrull:
Fin Fang Foom (Main)
Multiple Man
Ryu
Meteor Smash is -21 on block. Elastic Slam has 21 frames of startup. See what's coming? Smash all over the screen with infinite X-Factors thanks to FFF, XFC the recovery, and tick throw your opponent. It's pretty much unstoppable once the Meteor Smash is blocked. If Meteor Smash hits, XFC it anyway into a launcher, and get a full combo on your opponent for huge damage. Skrull has infinites in X-Factor, so you don't really have need for Inferno - especially since he no longer has the best line in the game during it. Ryu provides a huge damage boost to make downing your opponent even easier.
Dormammu
Mephisto (Main)
Multiple Man
Kingpin
I'm not confident that this is Dormammu's best combination. Basically, Mephisto provides excess meter, and Kingpin boosts the damage on semi-random Chaotic Flames and Stalking Flares. Dormammu can link Chaotic Flames via Purification on any assist he touches, so that option is pretty much locked off. I've also considered a Godot setup for him for countering FFF decks, but that would mean having to burn 2-4 bars of meter at the start of every match to get down to 0 meter, and that might be difficult against some of the more aggressive teams.