Right now frontline melee fighters have two directions - Shieldbearer and Paladin - defense oriented route, or Knight and Deathknight - offense oriented route. Unfortunately these routes are a bit restrictive when it comes to Character Fantasy. It's a bit strange that all characters must choose between a Boyscout class and Evil Cackling Villain class. I propose adding a third class that is, let's say, less ideologically alligned

Warmaster: +15 HP, +10 Attack, +10 Defense. Requirements: Either Knight or Shieldbearer.
Unique Ability: Combat Focus - when activated, next non-spell skill becomes Instant (3 charges)

Also, somewhat unrelated, but  I think Paladin needs a buff. Currently it feels quite situational and it is significantly less interesing than Death Knight's. I think that the only reason people pick it is because they already choose Shieldbearer. Maybe give it an Active Skill that somehow buffs all allies? Or some AoE Light Attack that targets a Column to complement  Holy Lance? 

Technically, assassin and spellsword do count as melee classes as well. 

They are but they also very different Character Fantasy-wise. Plus they have their own gameplay quirks that are not very compatible with the Pure Muscly Fighter role. 
If you go for spellblade you need to invest in some other Magic classes, and propably look/craft equipment that boost Magick Attack alongside regular Attack

If you go for Assassin you should at least consider "In the Shadow" because otherwise you're ignoring one of the Major bonuses of that class, and also you'll need to take off your Plate Armor and at that point you're no longer a tank. You can function as one if you then pick Ninja and start stacking Mag Def and Evasion, but character fantasy. That character would be some sort of Ronin who keeps easily dodging and parrying enemy attacks before retaliating with his sword, which is also cool, but a different kind of cool compared to an armored juggernaut that swings a big stick and shruggs off everything enemies throw at them

Also technically Assasin is not strictly melee class. It works fine on Archers too