I feel quite the opposite
Apart from very few classes I'd say most heroes are potentially
equally useful. The problem is some classes are more versatile and all around decent, while others are more specialized and niche. Hellion and Crusader are definitely great and they work with every team and in all circumstances. Leper on the other hand needs right set up to shine, he needs proper trinkets or even quirks, but if he gets what he needs, his dmg is devastating. At lvl 6 with 50% dmg buff he deals up to 39 dmg, while Crusader and Hellion - 28. Leper's Hew skill has more or less the same dmg while hitting 2 spots.
What works in apprentice dungeons, not necessarily works in veteran or champion dungeons. Same with light and dark runs, I definitely wouldn't take Leper for dark run without very high scouting chance, cause when he gets shuffled he's screwed. But in light runs, combined with Jester spamming Battle Ballad which buffs speed, accuracy and crit, Leper is a king.
PS. Week 58; all important buildings fully upgraded, most of bosses killed, so far 6 heroes died (including 1 Legend Bounty Hunter), not even once used Abbey or Tavern. I think I'm ready to assault the Darkest Dungeon
