So, I've been doing some math with the new 4.12 patch, and I still agree that w should be maxed before q when jungling (however, you should still start with q at level 1). Here's the proof:

When considering what skills to max for Kha'Zix, one should focus on the advantage that is given to jungling/farming (just trust me on this for the next bit, and you will see why this is the case). Since his raw early game power is not as insane as it was before the 4.9 patch, Kha'Zix needs an advantage by a means other than easy early kills which are not so easy to get anymore. This means he needs to do more farming. So when I talk about his skills - mainly his w - I will be doing damage calculations with regards to farming in the jungle; in other words, referring to damage per second or farm rate.

Here's some base information and calculations:

q damage (to non-isolated targets) is:
70 / 95 / 120 / 145 / 170 (+ 120% bonus AD)

q DPS (i.e. q damage divided by the static cooldown of 3.5s) is:
20 / 27 / 34 / 41 / 49 (+120% bonus AD*0.29)

w damage (to monsters) is:
90 / 138 / 186 / 234 / 282 (+ 120% bonus AD)

w DPS is:
11 / 17 / 23 / 29 / 35 (+120% bonus AD*0.13)

So, when considering maxing q versus w (from levels 1 to 13):

DPS when maxing q is:
20 / 31 / 31 / 38 / 45 / 45 / 52 / 58 / 66 / 72 / 72 / 78 / 84 (+120% bonus AD*0.41)

DPS when maxing w but starting with q at level 1 is:
20 / 31 / 31 / 37 / 43 / 43 / 49 / 56 / 62 / 69 / 69 / 76 / 84 (+120% bonus AD*0.41)

And taking the difference in DPS between maxing q versus maxing w is:
0 / 0 / 0 / 1 / 2 / 2 / 3 / 2 / 4 / 3 / 3 / 2 / 0 (+120% bonus AD*0.41)

In summary, there is not much of a difference in DPS when maxing w versus the so-called superior 'maxing q'. HOWEVER, THIS IS JUST RAW NUMBERS. YOU MUST TAKE NOTE THAT w provides area of effect damage, thus increasing clear speed of camps containing groups of monsters as multiple monsters take damage simultaneously from your w. And furthermore, you have better sustain as w heals for a significant amount (40 / 70 / 100 / 130 / 160 (+ 50% AP)), which means you can spend more time in the jungle to farm for gold and experience, and be more readily available to gank with higher health.

Now some people may argue that w is a skillshot, and that when ganking, you're not always going to be able to nail your w compared to your q and that you're not fighting monsters to provide your w with the +20% bonus damage. True HOWEVER, your early ganking skills aren't as strong as they used to be, and after level 6 (in which case you evolve your q) you should be have much less of a problem ganking and dishing out the necessary damage. Also, keep in mind that you should NOT be poking from afar with your w at early levels (which is completely stupid), and should rely on short ranged w casts to ensure that you nail those skill shots and have the AOE slow to follow up with q's and auto-attacks.

With this evidence, I hope that people will open their eyes to see the way of maxing w when jungling, and maxing q when laning.

P.S. Thank you Riot for buffing Kha'Zix, and for clearly making him a balanced champion. I now consider Kha'Zix to be in the top 7 junglers, whereas in 4.9 he could just barely be considered top 10.

Why do you not switch out the SotEL with a bloodthirster in the lategame when fully build, and if so what is your reasoning, personally i use it when im against super squsihy targets with little armor, to further boost my isolated-q burst (though i do it with CDR runes) and basically reach a point at which i can 1-combo squishy targets. Besides this, nice guide and good reasoning.