I don't think that Kha'Zix's current buffs will be of much use

Kha'Zix had his base armor increased on the PBE, also his Q costs 5 less mana.

Buffs are buffs and they're always welcome, but I don't think they will solve Kha'Zix's main problems.

The mana cost reduction is nice, but Kha'Zix doesn't really have mana issues. The only time you have mana issues as Kha'Zix is when you max W and spam it. That's why, back when it used to proc Kha'Zix's passive, you would build a Tear of the Goddess. However, outside of this situation, Kha'Zix doesn't have any mana issues, provided you can manage his mana correctly

The base armor increase is extremely welcome. Not only it allows Kha'Zix to lose less health when clearing camps on the jungle, but he will also have an easier time laning against AD champions (should you decide to use lane Kha'Zix).

There is a problem with those buffs, however. They don't solve Kha'Zix's main issues. One of them is that thanks to 's nerfs, Kha'Zix has a harder time clearing camps on the jungle and waveclearing in lanes. However, the biggest reason why this was such a big hit to Kha's performance is that he can no longer now waveclear to get someone isolated. He now completely relies on catching someone in the jungle. Either that or making sure that his allies have waveclear.

You can solve the above problem by evolving and maxing W, but there comes another issue. If you don't evolve Q early game, Kha'Zix is completely worthless. His burst without evolved Q is absolutely pathetic. Evolving Q is pretty much mandatory unless you are behind and your enemies are constantly grouping. You can't max W second, since you really need the extra range and resets from E. So you don't evolve W until late game, where it becomes less useful as a waveclear tool. This really hurts his viability at laning. You would think that this problem would be solved by just going jungle with him, but there is another problem in the jungle. Kha'Zix's clears are surprisingly slow. Without Tiamat's power, he can't clear camps fast enough, and if he is being counterjungled, he will have to rely on ganking to compensate that. But Kha'Zix doesn't have good ganks.

There is also a third issue with Kha'Zix. His R evolution is completely useless now that the damage reduction has been removed. Unless you are a god of hitting skillshots, there is no reason to evolve R over W, whose evolution isn't that good either, but is the least bad out of his 2 last options. I honestly don't have any good ideas to make it worth to evolve over W without making it a mandatory evolution. One idea would be to allow Kha'Zix to gain armor and magic resistance during a duration. This could work as a means of reducing damage done without being actual damage reduction. And thus, enemies could counter that. The counter would be penetration. The problem is that changes to armor penetration items make it a less appealing idea, since all armor penetration items are niche now.

I trust on Riot and I hope that they have better ideas to solve Kha'Zix's main problems on a future patch. But those buffs are going to be good.