Actually the first Willbender Flames change would be the most potent one by far, I am not seeing how changing swiftness to superspeed or increasing F2 healing or some auto-attack modifiers is considered broken and demanding „ezmode“, when Willbender is by far the most underperforming spec out of the entire expansion and can‘t in no way compete with other roamers such as Heralds for example.
Also changing condition damage increase on Lethal Tempo to crit chance increase would be an insane damage buff, since Willbender lacks the passive burn application Core Guardians have and since Willbenders don‘t have easy Fury access unless they sacrifice alot of damage and pick the Valor line. Also I believe you really don‘t get the point, since it would be a change that targets the low 11K health pool of guardian and would enable us to play more defensive amulets, meaning it would be a sustain buff. We know for a fact that Power Core Guard was a viable roamer when resolution increased crit chance by 50% back in the day - Lethal Tempo being changed would open up exactly that playstyle again.