PvE
Willbender is probably the most gameplay changing of any EoD elite for now. We get access to exclusive physical skills, which is a different gameplay from what we've played in the past. We keep the traditionals virtues F1-F2-F3, but the setup for skill is based on attacks and counter-attacks. This said, we kinda rely on positionning and fast reactions, which goes to anticipation. Some skills actually bring what is needed : "Symbol of Blades" with teleport to target, F1-F2-F3 enabling a long patern of possible fight phases, and utility skills. Meanwhile, I think we're kinda lacking of real sustain, since of Virtues once used or traited with "Phoenix Protocol" are no longer effective in Regeneration and can bring us to a really squishy spot, where we don't really know what to do excepted escape. The elite skill "Heaven's palm" need few boons like protection to bring on the possible for some complicated situations where we have to have certains mechanic bosses. Overall, I'd add some exclusive effects on the skills, like you did for F1, but with more impacts on the visual design and animations.
Willbender brings an emotional and adrenaline creator class, but it still need some support for longer fights. Aegis, swiftness, quickness, and protection. I'd add a second stack of Stability for the F3, since it's really easy to debuff with the previous expansion.
The skill 4 "Executionner Brawlong" is kinda low on effect and not really impactful. I'd see a circle that could potentially pull up enemies, making the actual fight more in phase with the actual Samourai 's spirit.
Otherwise, there's a synergy with all traits, but it might be difficult to find a condi build with this specialization. i'd add few condis to some basic skills, with a special trait that could potentially build a real gameplay versatility.
WvW
As for other classes of EoD, we need to bring the small scale fun gameplay to a level of large scale fighting.
Few ideas : increase the radius of certains skills, decrease some cooldowns for WvW, and as for other classes : a visual marker on the ground.