Right now I feel if you do not play Reaper you aren't doing decent damage in comparison. Ranged makes sense to do a little less damage since you have a lot more freedom, but other melee shouldn't be this weak in comparison.

Dragoon:
Raiden Thrust > Vorpal Thrust > Heaven Thrust > Fang and Claw > Wheeling Thrust
280 > 280 > 480 > 300 > 300 potency means an average 328 potency per weapon skill

Samurai:
Hakaze > Jinpu/Shifu/Yukikaze > Gekko/Kasha
180 > 280 > 370 (over 8 weapon skill is 2120 / 8 = 265 average potency), but due to passive 13% shifu/jinpu speed/damage and able to skip to last weapon skill with Meikyo Shisui is actually closest to on par with Reaper.

Ninja:
Spinning Edge > Gust Slash > Aeolian Edge
210 > 320 > 420 potency means an average of 316 potency per weapon skill (371 effectively with passive skill speed huton provides)

Reaper:
Slice > Waxing Slice > Infernal Slice
300 > 380 > 460 potency means an average of 380 potency per weapon skill (418 effectively with Death's design). This doesn't include the use of off global cooldown Blood Stalk/Gibbet/Gallows and Enshroud when they can do 520 potency every 1.5 seconds for 15 seconds.

Now you might say Dragoon has more AoE, but even AoE combos fall short.
Doom Spike > Sonic Thrust > Coerthan Torment
110 > 120 > 150 potency means 126 average potency per weapon skill

Reaper on the other hand...
Spinning Scythe > Nightmare Scythe
140 > 180 potency means 160 average potency per weapon skill

I think the biggest changes needed are making melee classes more unique while adding some potency.

A few examples:
Monk has 20% speed due to Greased Lightning III. Give them 40% attack/skill speed to make them do really fast weapon skills vs stronger ones. This would give a whole new feel to Monk. Going from 2 > 1.6 seconds to 2 > 1.2 would feel much faster and rewarding at the higher levels.

Dragoon is all about Jump so maybe make more damage based off Jump cooldowns. Make a branching ability based off Jump and transition to single target or multi-target to give variety for large group vs boss. Like...
High Jump 400 potency followed by Mirage Dive 600 Single Target Potency
High Jump 400 potency followed by Stardiver 300 AoE Potency

Samurai you could remove the cooldown of Kaeshi: Setsugekka or make Meikyo Shisui reset cooldown of Kaeshi. Another thing is third eye rarely is used and Samurai is a DPS so why not put an offensive aspect to it like adding a mini Meikyo Shisui or add Higanbana effect to next weapon skill.

Ninja I liked Forked Raiju/Fleeting Raiju after using Raiton. Maybe add weaponskills that can be used between ninjutsu with a cooldown so you are rewarded for not doing them all at once. The bunny is funny, but annoying if lag means you mess it up and you can lose A LOT of damage when it happens. You could make the ninjutsu all draw from the same cooldown, but just use the Doton Ability rather than doing Ten→Jin→Chi for example.