Lethal Tempo is bad design
I went Lethal Tempo Yi top vs Conqueror Tryndamere
I was able to kill Tryndamere twice. The 1st time was early game at 2 minute mark and. 2nd time is lategame when he didn't use his ultimate. Otherwise he completely obliterated whatever the hell he wanted and no one could duel him. All because he had Conqueror and I had Lethal Tempo
So I decided to ignore him for the rest of the game and farmed other lanes, the jungle. Then I killed I went mid, killed velkoz before I even get any benefits from Lethal Tempo itself.
So Either I get obliterated by Conqueror Tryndamere or I kill enemies before I even enter in Tempo mode.
1.5 seconds to wait in battle is pretty much the life time of a fight. The only guys who get the benefit are the once that have durability or are ranged champion like Vayne who is untouchable because of stealth and her hard cc
4 seconds is quite a lot for Conquror but at least you get huge amount damage and you can push the lane slower so you able to keep it all the time.
Attack speed by it self means nothing if you don't do any damage