I’m sure this has been mentioned plenty of times, but there are far too many classes that are unusable because their traits and talent trees are garbage.
Pretty much everything at level 100 sucks except Fireblade and Fortitude, and needs to be replaced.
As for class traits, here are some suggestions:
Assassin:
-Deal double skull damage to poisoned enemies.
-Matching skulls attacks the last troop rather than the first.
Bard:
-Give yellow troops 2 mana per turn.
Deathknight:
-Deathmark a random enemy when one is slain.
-Summon a random undead when an enemy is slain.
Diabolist:
-100% chance to summon Nightmare when an ally casts a spell.
Doomsayer:
-50% chance to Deathmark on 4/5 matches.
Heirophant:
-100% chance to cast a random buff on an ally every turn.
Knight:
-Gain barrier on blue matches.
-Move to top position when an ally takes damage to life.
Necromancer:
-Add 50% of total souls collected to magic.
Oracle:
-Centaurs start with 50% mana.
Sorcerer:
-Gain 1 magic on 4/5 matches.
Warden:
-Summon a leaf storm at the start of each turn.
Warlord:
-Reflect 50% of skull damage.
These are just some ideas, but these classes could use some serious buffs to make them more competitive and to give them more distinct flavor.