I think that Lee Sin ult's main problem is not the damage, is the cooldown

I don't actually disagree with the nerfs on Lee's ultimate on PBE. However, on my opinion the main problem is actually the cooldown, which is not only too low compared to other popular jungler's ultimates (Vi, Hecarim, Zac, Kha'Zix, and even Graves have higher cooldown on their ults, and many of those ults have a lower impact than Lee's ult) it is also too low for what it does. Not only his ult has very high damage, but its effects are potentially game changing, especially because Lee can change the direction of his ultimate by using Flash. His ult also has too many uses, ranging from picking off enemies, to escaping from enemies that are chasing you (as if Lee didn't already have lots of ways to escape).

Considering the fact that Lee can also get more CDR items than ever, he can make the cooldown on his ult even lower, especially compared to back when it was difficult to get CDR on manaless champions. He has access to three cooldown items that also give him high damage .

On my opinion Riot should increase the cooldown on Lee's ultimate to put it more in line with other champion's ultimates, especially other junglers. For example, Vi's ult has a 150/115/80 CDR at levels 1/2/3 respectively. Zac has 130/115/100. Hecarim has 140/120/100. Both Graves and Kha'Zix have a 100/90/80 cooldown on their ults, and their ults certainly have a much lower impact compared to Lee's ult. Why he is allowed to have a 90/75/60 cooldown on his ult when not only his ult has an higher impact, but also higher damage than all the aforementioned ults? (fun fact: Lee's ult at level 1 has a lower cooldown than Zac and Hecarim's ults at level 3)

They could even revert the damage nerfs on PBE if they just increased his ult's cooldown to a reasonable level.