while true more diana's mid than jungle, but yea neither are listed by riot as an assassin, tho they really play as assassins. As for Rengar in jungle he is fine, in fact better in jungle simply cause he needs that jumped surprise to work to his fullest, but his staying power in a fight is really really weak, vs any tanky AD jungle or even a decent AD carry in a straight up fight he falls incredibly short
So best rengar results are to make sure your team sets you up for a proper gank, clearing/notifying wards and being ready to CC someone or pull them toward tower, cause a rengar can nearly instakill a non fed/tanked up AD carry at lvl 6, esspecially with sheen, i have killed ashes and caitlyns who didnt know i was there in 1 second flat (best acheived by getting 5 fero, activating stealth/5 fero q slightly after, then pouncing just after the 5 fero build up from stealth, that way you can double empower q and regular Q all at once
its devastating
i know its off topic but yea thats that, as for khazix, if he is man based that will make it very different, but if he is CD only he is going to be VERY high mobility