Honestly, Maul isn’t so bad, he ramps up and does good damage, CD increase is fine… I think he just highlights how weak LV is as a GL. If they were going to do anything, CG could always just buffs his stats to high heavens but I think a tweak of his 3 moves is all that is needed, especially when in Ult. I’d have it as follows.
On his basic, I’d keep the deal damage again at 30 stacks but then have him damage again at 60 stacks instead of when in ultimate. Then, when is Ult, he attacks again just like his GAS counterpart. Keep in mind that the damage of this move of pretty atrocious until late in battle so this is a way to make it a bit better and later in battle, scary.
On Dark Harbinger, he needs a massive damage increase and honestly, have it mirror JMK to an extent. Instead of +20% damage on subsequent uses up to 100%, have it +50% damage up to 250%. For the ultimate version, have it double physical damage, sea true damage, dispel all buffs in target enemy and buff immunity cannot be cleansed.
For Unshackled Emotions, honestly the only thing I’d add is during ultimate, ally Mastery gain is doubled so instead of up to 60% mastery gain, it’s up to 120%.
None of these are insane compare to Kenobi… the basic scales nicely and becomes devastating late in battle (or in raids etc), his first special should ramp up and become something you’re scared to face if he uses it a few times then hits in Ult and the locked buff immunity will help against tanks and the doubled Mastery gain for allies while in Ult is just a nice increase but nothing crazy. These changes would make him fun at least, the basic would hit for up to 6 times in ult but since the damage is mostly low, it ain’t OP, and it would be fun to see how high you could get the first special to hit.