I disagree on you doing the frozen malet and trinity force....As trinity force alredy provides a chance of slowing the enemy champion '-'.About the healt the right thing is build a warmogs giving you more healt and dmg when you build atmas.
Just my opinion :)

Trinity is no good for him in my opinion. It's too expensive (4070) and only gives 30 useable attack damage. The magic damage only benefits your Decoy, which you aren't using for burst.

The passive on sheen is very good but the ability power is awful for him. And the passive with sheen is really lackluster without AD. And if you invest in sheen... you are pretty much locked into a trinity force which just doesn't pay off for him in the end because once again, while the passive is good... no AD to back it up means everything else suffers, and the passive just isn't as good as it could be.

The movement speed is alright and attack speed is ok but you get those both from nimbus strike. Burst damage is about popping cooldowns, attack speed is for sustained damage. You shouldn't really be chasing with him, that's what summoner spells and nimbus strike are for.

Cooldown reduction is also not needed since the cooldown on Crushing blow is only 5 seconds at max level.

Tforce is too slow, and it's just not worth the cost. +AD all night and day over tforce. You're better off turning your phage into a frozen mallet and getting an atma's impaler. Way better imo.

no Tforce :(

You make a burst build and don't use a trinity OR coll-down reduction....