Since the game start, some unit are up or nerf, but lot of them are forgotten since long time, and they probebly need to be little bit fix.
Of course, maybe some people will say about my idea “shut up, get out” (like JJ in spiderman movie ^^).
But, that cost nothing too write this …
(And sorry about my english, not my native tongue)
Carnex : Increase the % of the third legendary trait.
Dark Master : add too “9 damage” a (+magic) or increase damage of spell.
Dimetraxia : Increase the % of chance of burning everyone.
Dokkalfar : Increase damage of spell.
Druide : Increase damage done to adjacent ennemies.
Dwarf lord : Give more armor when ennemie dies.
Ifrit : Increase damage of spell or burn one more unit.
Keeper of soul : Increase the % of summon Wight to 100 (Wargare are almost stronger as Wight, and they are summon to 100% by Kerberos).
Night terror : Increase the amount of magic steal.
Ogre : Add damage to the spell, (or add something else please, they are so lame… poor ogre!!).
Owlbear : Increase the reduce of attack.
Peasant : Increase the power of spell (or their “troll” power!!!).
Rex warrior : Increase the amount of attack gain if ennemies dies.
Rhynax : Increase damage done to adjacent ennemies.
Sheggra : Change third trait (Right now, this is quite useless, maybe change like “deal 3x damage too burning unit” (or something else)).
Sir Snothelm : Change second trait (if you use gobelin team, you will never ever make sick ennemis (sooo, that is not really usefull.) So maybe change as “Disease a ennemie with skull damage”).
Steam Turret : Increase the damage done of the spell, or add some effect.
Tankbot 2000 : Increase the amount of armor stollen.
Tassarion : Remove the “Can only be cast once” (I never ever saw this unit in pvp, meaning maybe what i think : no one love this poor wizard!!!)
Vampire Lord : Increase the amount of life gained.
Warlock : Increase damage of spell or add a effect (Same spell as Knight Coronet but really less powerfull)
Trait : Invigorated : 1 more life gain when ally make a spell. (Just get one little point of life is not really usefull (sounds like someone is too much greedy to help unit!! 
))
Well, maybe im wrong about some unit, but definitly i think some unit need more love from the dev!! 
Have a good day!!