Shen mini rework: Bring back the ninja

In his current state, Shen scales with some awkward combination of AP, health, attack speed, magic pen and resistances, and there's nothing very ninja-y about him. These are my thoughts on creating a better, more unique Shen.

Ki Strike: Replace the HP scaling with percent current health damage. Ki Strike otherwise stays the same, except that it may give better sustained damage with the new Feint.

Vorpal Blade: No more AP scaling. Shen's auto-attacks against a vorpal bladed target apply a very weak, but stacking slow, giving him the ability to stick to targets, or peel for carries while giving them regen.

Feint: Just like with Vorpal Blade, no more AP scaling, and basic attacks no longer reduce Ki Strike's cooldown by an extra second. Shen's shield scales (gradually) with his bonus HP. Until Feint subsides or is broken, it also gives Shen an attack speed buff that scales with his resistances (also very gradually, to account for 400+ resistance Shen lategame)

Shadow Dash: No more AP scaling (patterns are fun), and no more damage reduction for taunted targets. I'm going to use numbers for this next part to simplify the explanation, but the exact durations here are not entirely important. Activating Shadow Dash gives Shen bonus resistances for 3 seconds. Shadow Dash can be instant cast to be used as it currently is. However, charging Shadow Dash for 1 second will stealth Shen for 2 seconds or until Shadow Dash is released. Charging Shadow Dash for 2 seconds will also give Shen a 1 second movement speed buff. If Shadow Dish is charged for 3 seconds, it will be cancelled and Ki Strike will be refreshed if on cooldown. Charging Shadow Dash should have a visual indicator, taking away the surprise factor if Shen chooses not to instant cast. Edit: The stealth and movement speed could be switched, so the movement speed is 2 seconds while the stealth is only a 1 second window

Stand United: A portion of Stand United's shield is applied instantly; the size of the instant shield is decided by Shen's bonus HP (Note: The entire shield value remains the same; the scaling only increases how much of the shield is immediate). The remainder of the shield ramps up over the 3 seconds that Shen channels Stand United. Also, charging Feint before casting Stand United will cause Shen to appear in stealth for 2 seconds and his next auto-attack to stun.

I would of course expect some nerfs to his base health, his shield base amount, and his base damages to compensate for the fact that these changes are definitely a buff overall.