Initial thoughts (general PvE, though some will apply to sPvP/WvW as well):
TL:DR: Spec has mobility, but doesn't have anything to follow that mobility up with. Skills are clunky. Traits are largely a set of bad trade-offs with some being obvious upgrades. Animations, VFX, and SFX are ok.
None of the Willbender Utilities can be used underwater.
-Off-Hand sword skills feel bad.
Sword 4 is slow. Its almost feels like its not worth using at its current animation speed.
Sword 5 fails to best-effort shadowstep toward the target unlike pretty much every other teleport attack.
-Virtues aren't that usable.
Willbender Flames' damage is low. Virtues are giving up a lot of utility for what is basically extra damage and boon procs, but the damage just isn't there, and the procs can sometimes be hard to come by.
Trading their passives buffs/boons for actives and triggers is fine, but the odds of triggering them against anything mobile is near zero.
F1 is super clunky. The lag time between the dash and the punch is enormous. The range is also not great.
F2 is mostly just a condi cleanse, unless you take Phoenix Protocol.
F3 Honestly, not entirely sure why its a shadowstep.
-Right-side skill bar skills
Reversal of Fortune: It only stops the damage, none of the secondary effects, such as knockdowns/knockbacks/conditions. The healing is laughably low if you don't get hit. Honestly not sure why I should take it over Litany of Wrath or Shelter.
Flash Combo //Repose: Flip-over skills needing everything to hit are fine, but where's the payout? It is significantly weaker than Fist Flurry in exchange for what, a shadowstep and a return shadowstep? Feels like it needs something more, maybe unblockable or cripple.
Roiling Light: Honestly, needs to remove movement impairing effects like most backwards evade skills have. That's my largest complaint.
Whirling Light: Feels like it needs more damage, and/or longer range. Animation is cool though.
Heaven's Palm: Range is short, damage is low, utility (KD and KB) honestly aren't worth the cooldown. 4sec KD in PvE is largely pointless, and overkill in PvP (if its not immediately stun-broken.) Animation is ok. Feel like the hand needs to be a bit larger though.
-Traits
Adept tier: I would only use 2 of these.
--Boon Pact: Useful with Phoenix Protocol. Spec is already fairly selfish, seems like the obvious choice.
--Power for Power: If not going Phoenix Protocol, seems like the obvious choice.
--Conceited Curate: Honestly don't think this is worth taking.
Master tier: Somewhat usable.
--Restorative Virtues: Largely only good if you're constantly cancelling active virtues.
--Holy Reckoning: I guess it would be good against hordes of enemies? The damage increase doesn't mean a lot since Flames don't have high base damage anyways. The healing obviously scales better with more targets. The problem is that the spec wants to move around, while Flames wants you to largely sit in one spot and have your target sit in one spot.
--Vanguard Tactics: I can see it being usable for the extra boons, and Resistance on shadowsteps is nice. Related: you need to update the guardian teleport skills of Symbol of Blades(MH sword 2) and Judge's Intervention to say they shadowstep.
Grandmaster tier: The good, the bad, and the ugly.
--Phoenix Protocol: This feels like an obvious PvE choice. the healing on Resolve is not great, and trading it for Alacrity honestly feels like a clear upgrade. Probably will be pointless in PvP as you won't be able to trigger it very often.
--Tyrant's Momentum: Honestly, the damage buff probably isn't worth the trade-off of harder to maintain stacks. You gain a 10% increase in damage for a 33% reduction in buff time. Yes, it is theoretically offset by Justice having a 2 second longer duration, but you need to be proc'ing it for that to matter.
--Deathless Courage: Going to be honest; haven't played with it, but it looks bad. You are trading a guaranteed block (1 aegis from activation, and X number of proc aegis) for the ability to not go into down-state. You are trading negating 1 attack and all its secondary effects for not going into down state. I am struggling to see a scenario where this is a good trade-off.