I am a Yi main and let me inform you that what you are talking about is bullshit.
Yes, Jungle respawn timers are increased by 30 seconds. The other thing that has increased is clearing time, jungle monster gold, exp, damage and tankiness. So not only does your full clear give you more than it used to, you can still permaclear even though the jungle timers have increased.
Then there's the fact that machete has been buffed, the on-hit aswell as the lifesteal. And we all know how awesome the synergy is with his passive.
The only nerf I can see is that Youmuu's lost its attack speed. That is made up by the fact that Maw is now a better item on him though, now that it gives CDR and now that Lifeline gives AD.
And now let's go over to the next buff. Fervor now gives AD per stack rather than on-hit, and while the on-hit was awesome combined with his passive, the extra AD synergizes really well with his Q and E ratios and synergizes even more with his crit build. The other buff in his masteries - Bounty Hunter now gives 1.5% extra damage per kill instead of 1%.
I'm not saying these buffs are huge but he's still far from getting nerfed again.