As a jungle Kench, my early game lives or dies by how much attack speed I get at the start of the game. Losing the 11% attack speed is complete crap compared to the options you allow me to take to substitute it with. 6 AD or 5 armor is not nearly enough to compensate for the lost damage from Tahm's on hit damage, that's not even counting the minimum extra 0.22 seconds it will take to stack the passive so that you can stun with Q.
I feel like the flex option is not nearly flexible enough since only one option is available for those who want to spec into more damage. A second 9% attack speed node would be greatly appreciated in that slot. Hell, if you're worried that double attack speed will just be the go to for AD carries, nerf them both down to 8% attack speed and it'd still be much better than 9% AS + 6 AD.