Silent Spirit can be used in Titan Temple, Campaign / Elite and Expedition. His Magic Resist needs to be buffed, and maybe his HP and Armor.
Raging Revenant can be used in Aurum stage 3 in Boss Pit and the physical-only Challenge.
Dark Horse and Legendary Brozerker can be used together for campaign / Elite levels and Mountain levels with suicide bombers. If the top two difficulty levels of Challenges have suicide bombers, they can be used there as well.
Legendary Brozerker can be used in the magic-only Challenge difficulty levels with crabs.
The sign-in front line tank hero for January, Vile Bile, might be useful for Fight Pit and Coliseum, to make all enemies attack her and absorb damage from all enemies for 6 seconds with her White skill, hit the enemy team with the absorbed damage from her White skill with her Purple skill upon her death, and drop a poison pool on the ground that the enemy team will take damage over time from if they walk through it with her Blue skill, upon her death. She just has to survive long enough to use her White skill.
Dragon Lady needs to have all of her skills redone and her stats buffed, Dark Horse needs his shield skill massively increased as well as a great Orange skill and a stat buff, Savage Cutie needs a great Orange skill like a passive Lifesteal boost or an Orange skill similar to Rabid Dragon's, and a stat buff, and Snap Dragon, Orc Monk need stat buffs (HP and Magic Resist for Snap Dragon).