Mocking shout should be a long range expanding cone instead of a moderate range instantaneous circle

I will explain in this thread why the suggested change not only is more interesting to play against, but also provides Tryndamere with more interesting play making abilities.

The current counterplay to the slow on the mocking shout is to turn around just as Tryndamere is about to cast it-- but that necessitates moving towards Tryndamere briefly in order to turn your champion around. So either you are slowed and he catches up or you move towards him and he catches up, which is a false decision (one of zileas' anti design patterns). That wouldn't be so bad if the ability were telegraphed better but the cast animation can be so subtle people may end up turning to face Tryndamere (inevitably moving towards him in the process) multiple times without him ever actually casting the ability. If mocking shout is going to have this pattern, it should be implemented in a way which creates more gameplay.

It would be more interesting to play against in lane because being a cone makes it hard to aim in melee range and makes maneuvering in melee combat against Tryndamere to juke both the AD reduction and the slow of his debuff a thing. (right now only the slow can be avoided) You use your dash creatively to avoid the debuff in lane just as he casts it by staying in the "sweet spot" where you have just enough time to dash to the side out of the way of the wave before it can hit you, for example. Aside from that it gives a bit of a time buffer if he is using it to chase you and you can't avoid it, and you still avoid the slow by facing him as the shout-wave moves through you.

It would be more useful to Tryndamere for the occasional team fight at baron or dragon or chasing down an enemy team because the additional range means he can debuff people to assist his team mates without putting himself in the middle of the enemy team. That is valuable to Tryndamere because it means he can access the power of mocking shout's attack damage debuff on important targets without being so close to them that he would end up being focused and forced to use his ult. The speed of the shout as it expands should probably be about the same as anivia Q, and the range should probably be about double what it currently is with probably a 90 degree angle.

Jungle Tryndamere would have a little easier time in ganks because though the shout would be telegraphed, being forced to turn towards the wave for about one second to prevent the slow may still be just enough to make a play happen.

It would be more telegraphed so there is time to adjust your positioning and react accordingly, and the wave itself is slow enough so that you can face Tryndamere while it passes through you and then turn around and keep moving. The choice in this case is real-- either face the wave until it passes through you (probably about 1 second) or be slowed for 4 seconds.

That may seem on the surface to be a trivial choice, but consider this: most spells require you to face the direction you are casting, and if a practiced Tryndamere casts his shout at just the right time he can force you to decide between casting a spell at the precise moment you need to and be slowed by a huge amount for a long time, or to wait and cast it a little late but not be slowed. It is subtle, but it is a lot more gameplay than the current mocking shout, and even this is telegraphed by Tryndamere's positioning-- which would have to be a flanking positioning in order to use this tactic.

Also consider that if the wave hits you then your attack damage will be debuffed for a large amount regardless of whether or not you are facing it, so seeing Tryndamere's slow moving mocking shout moving towards you puts an impetus on you to unload your important attack damage scaling abilities before the wave arrives or to back off with the intention of waiting for the debuff to expire, which again is a lot more gameplay and interesting decision making than the current mocking shout which simply applies the attack damage debuff instantly regardless of which direction you are facing and which gives you no time to react aside from its short cast animation.