I was watching the Patch Rundown for V5.11 and the rock-paper-scissors argument of "Squishies versus LeBlanc versus Tanks" or, more specifically, the hypothetical matchups between Lux/Vel'Koz and LeBlanc and how her Distortion speed sits in a sort of binary space where she's either fast enough or she's not and... it got me thinking.

We want squishies to make a comeback (god I miss Brand); but we don't want assassins to go back into being useless. So why not make the relationship more dynamic rather than binary? Rather than LeBlanc is either fast enough to win her lane or too slow to be viable.

Why not make dash speeds scale with hastes and slows?

Vel'Koz lands his Plasma Fission on LeBlanc as she makes a reckless charge without thought of her positioning and he reduces her Distortion's dash speed by 70%, allowing him to dodge to the side and land his own Tectonic Disruption and win the trade.

Why not make it so that immobilizes all innately apply knockdown? (similar to Event Horizon)

Lux throws out Light Binding as LeBlanc, again, makes a reckless play without thought for the consequences (because she's used to not needing to plan her opponent's reaction) but gets rooted - knocking her to the ground and interrupting her Sigil+Distortion combo in its tracks.

• Immobilizes that currently do knockdown: airborne, stasis and suspension (+a few special-cased stuns).
• Immobilizes that currently don't knockdown: stun, root and suppressions (-Nether Grasp, which is special-cased).

And I'm not just suggesting this for LeBlanc. All dashes. (Distinct from blinks, just to clarify, so LeBlanc's retreat would still be instant).

Accommodating changes:

• At the moment, movement speed slows are hard capped at 110 and hastes are soft capped above 420. However, if you imagine going up against Thresh's 99% slow, a dash would be no faster than walking as both would very easily be reduced to nearly 110 - which isn't right, dashes should always be superior.
• The neatest solution would be to have a base dash speed and a (+X% total MS scaling). This can be shown in the tooltip (e.g. "LeBlanc dashes at X speed to the target location") and as easily variable between champions. The base should be low and would reflect the lowest potential speed, while the scaling should be high (easily 200%+) so that slows and hastes heavily affect it. So LeBlanc's Distortion speed could be 930 (+200% total MS) for 1600 with base MS, 1250 versus Vel'Koz, 1153 versus 99% slows and 1776 with Ghost. (suddenly Ghost is an interesting spell, although maybe not on LeBlanc). For a dash that should have low variance: increase the base and lower the scaling.
• An alternate solution would be to apply hard caps to movement speed slows and soft caps to movement speed hastes, as with standard movement (if your raw speed is below 220, it is halved and added onto 110; while if your speed is above 415, the amount in excess of 415 is reduced). The exact amounts would probably need to be relative to the base dash speed - i.e. if Distortion has a base dash speed of 1600, the lower cap could be "anything below 1056 is halved, and added to 528" (66% and 33%, respectively, which matches 220 and 110 assuming 330 base speed).
• Forced Actions (Taunt, Charm and Flee) currently do not directly interrupt movement and so shouldn't interrupt dashes. However, their duration should be queued until the target is able to act - since charming someone like Lee Sin wastes a good portion of the charm duration, which isn't fair considering you managed to land the charm in the first place. Alternatively, it could just interrupt as if it were a direct immobilize - you kiss Lee Sin out of his Resonating Strike, saving your ally in the process!
• "Jumps" could be made distinct from "dashes" in that they are unaffected by hastes and slows, and perhaps also the proposed change to immobilize. Rocket Jump, Unseen Predator and Elastic Slingshot (for example) would have a fixed speed, regardless of slows and hastes, and will ignore immobilizing effects (except for explicit knockdown/airborne effects). So using Dazzle on Tristana will not bring her crashing down, but Ghost will not benefit her either.
• "Leap" abilities would be case-by-cased into either the "jump" or "dash" category. "Leap Strike" should probably be a dash while "Leap" should probably be a jump.
• "Spinning" champions currently face in the direction they are/were last moving, and this is a recognized limitation of the engine. However, would it be possible to special-case "Mocking Shout", "Backstab" and "Petrifying Gaze" to consider spinners to be facing in all directions while spinning - so Cassiopeia one-ups her sister while Tryndamere will fail to mock Garen or Wukong (whose damage would be affected by the AD reduction, regardless of what position they think they're facing).

The opportunity for "special cases" would still exist. Dashes that are immune to crowd control should probably also be immune to slows, but not necessarily - e.g. Assault and Battery could remain immune to immobilizes but now be affected by her movement speed (for better or worse). Thresh's Dark Passage, despite being a dash, could be immune to slows and hastes (or affected by his speed instead of his target's, or vice verse). Dashes that are immune to crowd control could also be immune to the positive effect of hastes - e.g. Nocturne doesn't have to dash faster if he ghosts.

https://youtu.be/8Wk6MowYtpw?t=5m