Twitch Kappa has now been out for 2 weeks and it's obvious he's less than good. A mediocre clear, an unreliable CC, a disperse ult (always a tricky type of ability) and no real advantages over other guardians. Let's take him apart, shall we?
Well, his 1 for starters. Mediocre to good for clearing a wave, great for camps. The problem is, it's his main damage output, but does poop damage lategame (barely a 100 to tanks). And his Kappa is just so weak. First 2-3 levels, it can help with waves and camps, but after that it does around 60-70 damage each hit and can be killed rather easily. Not exactly optimal. Especially considering that if you play supp, you're always behind.
His 2 is ok. Helps him dive into fights to deal some damage, but is unreliable to useless when it's not a big fight, since it requires opponents attacking him. Not really much to say here.
His 3 is the second biggest problem after his 1. Mediocre damage (like a CC ability should have), but hitting it is unreliable because the targeter is smaller than Kuzenbo's model. Significantly so. For an ability that already has limited CC and which design makes it a small challenge bringing people to your team, impossible even when you stand in front of your team, the small targeter is a major problem. Using it to push people away and dive is an option, but the 2 doesn't offer mitigation, it just reflects damage, it makes you very vurnerable. Plus, you can only CC a single person with this single CC ability on Kuzenbo.
His ultimate though is strong. It's a bit difficult to use to bring people in, but it's excellent to break up the opponents and it's a great escape. The damage is decent too.
In my opinion, the one needs both a small damage buff and a buff to the Kappa (preferrably small saling to his attacks) and the 3 needs a bigger targeter to actually be a reliable tool since it's CC has rather limited uses that require set-up.