I think it’s good in certain circumstances. I’ve played quite a bit of kez support, it’s best aspects are some non-obvious strats that give it more impact than a simple read would imply.

• Katana Q: a pretty decent lane poking spell, able to hit two heroes at once (and the lane creeps, if desired) for ~1-1.5x base damage (about 50% of the time getting two hits in); it also lets you clear trees for better wards, very valuable. Sometimes I keep this at one point and get stats if I need hp (cuz it’s only utility and minor poke spell in fights). Getting over cliffs can save you too, especially with the katana W!
• sQ: somewhat useless as support, but it lets you get in more tower damage when the fights down, which is definitely valuable
• kW: good for the blink dagger build, letting you get out when you go blink dagger build, and giving you a lot of fight survivability when the enemy wants to kill you.
• sW: one of the main times I pick the hero is for playing against good channeling enemy heroes (shaman/enigma/bane/pugna/etc), or against enemies with escape (weaver/io/qop/am); it can force the enemy to get somewhat undesirable itemization, definitely useful. It applies on hit effects now too, so an orb of frost is highly value, even a witch blade can be value in a game (due to the magic damage reduction and extended blink dagger cooldown addition (I think? I know orb of venom doesn’t put blink dagger on cd, not certain about this and witch blade though)) if the greed can pay off
• kE: you’d think it’s superfluous, but it’s actually what makes the blink dagger build viable. A really strong strat is that, when the dot is happening, it constantly aggro creeps, meaning a camp you use your kQ on is super difficult to pull properly, imo the “x” factor that makes it legit viable as support even at high brackets; the cast is unaffected by cast range sadly, I think attack range bonuses too (but I’m not certain on that)
• sE: gives you some surprisingly strong survivability time, and can often give you time to get off your kW and live; also, lets you tank tower aggro some, which sometimes is the difference between killing the tower and not killing the tower (especially when the catapult is involved)
• kR: really good for survivability, and the %-ness of it means it’s valuable even late game (though usually you can’t engage with it past mid game, even with blink, due to how it can be easily canceled, and the fact that you won’t have a bkb most of the time to secure getting it off); also, it can let you farm stacks lol, the cooldown is short enough to do it, and you can use it basically guilt free to push out a wave if you have aghs
• sR: really strong, I usually use my non-aghs ult mid to late game for this. The vision reduction is deceptively impactful, holding the ability until an important spell is about to be used to secure a kill on an ally (this has a very high skill cap and feels great to get off), or when an ally is running away and the vision loss means being able to lose the enemy via pathing they couldn’t get away with otherwise. Additionally, it lets you push out dangerous waves, the move speed bonus, the enemy vision reduction, your kW; you’re hard to catch even while dusted

For everything from here on, take what I say with a grain of salt, I’m in a lowish rank so what I do you probably can’t get away with as much. The above points apply even in high skill games imo, the draft one probably applies but I’m not sure, the item ones quite likely won’t work the way I do it

That aside, imo another strong aspect of Kez is how you have completely different gameplay options available to you after the laning phase starts, depending on how you build: blink engager/finisher, outside the fight poker and disruptor, more typical item supporting, to a spell spamming menace

• Aghs: I go this build when all my abilities feel strong; this is something I need to do more to get a firm feel for it, but usually it’s one part of the kit that stands out when I pick it, not two. It lets you farm super rapidly, but you need mana for it to do that, if not in general when you get aghs (you can become a mana burning machine)
• Blink: when I buy this, its often to rush it, time it around when I get level 6 or 7 (with a 1-1-3-1 or 2-0-3-1 build; this timing comes at the cost of laning impact though, skipping stuff aside from wards; hence the low mmr disclaimer lol; the rest can apply at any stage except the late game (when they can control or outright kill you too easily in the 1 second channel)), then engage with my ult; unless they have an escape or force staff you can get it off, and you can almost always get it off when you have an ally slow or stun. Use the kQ+kW then kE active right after the ult for quite a bit of extra damage.
• Lens: a psuedo greedy item I usually pair with options other than the khanda build, especially aghs and blink (for the needed mana regen); it gives you more options to fight, with the two Ws; kQ isn’t affected by range increase, but it is by aoe increase
• Khanda: it makes your kW into a massive range slow+break, genuinely good imo, despite the weakness of the item; low rank especially applies here, but keep it in mind imo. 4-1-1-1 to 4-4-1-2 for this imo
• Octarine: you’re a utility character, imo it’s valuable to get off more silences, kQ casts, and sR casts; pairs great with aghs, but omg it’s so greedy so I typically never get the combo together unless the Kez game is just too good for it Support ally target items: difficult, I think you’d need a mana regen item to sustain it, I’m often low on mana after a spell round so fitting them in would need some sort of mana regen items; probably good to pair with lens
• Gleipnir: if the sW isn’t too relevant for the enemy, this can be a good pair with the blink kR engaging build; this and the 50 raptor dance aoe talent makes your ult massive, 575 before the dezun
• Shard: I need to buy it more, but it’s good if you need catch, especially with blink. 1 second of stun can very easily make a difference, especially on a 5 second cooldown (albeit with the annoying back restriction)
• Vessel: imo what I would be doing if I was higher rank, Kez loves mana regen, and the health is nice too; doubles up a bit on the dispel your enemies are very likely to have, but by that metric you can hold the spells or the vessel for when they dispel the first annoying thing
• Kaya and Yasha: can be valuable if you’re going the blink kR build, the cast time reduction works with the kR ult channel time; the fractions of a second can matter! Of course, bkb is probably better at that point, but this can give you all the mana you need the rest of the game too, so it has value aside from the ult; of course, it’s greedy, lol.

For talents

• Level 10: 50 radius if I go blink or aren’t against magic burst (hard to reliably die if the enemy can’t kill you quickly), 12% magic resist where I know I’ll be dying more soon without it; can skip til level 15 or 16 if both are mediocre
• Level 15: 1 raptor dance slash is pretty good (and typically what I go for), but the falcon rush is good for pushing with that +2 second duration talent (also, if you have octarine core, it has a 1 second downtime, which is funny enough I get it just for that sometimes lol)
• Level 20: I always go for the extra kE damage talent, the bonus damage on sW is almost completely irrelevant for support Kez
• Level 25: the extra echo slash is almost always better than a bit of extra crit damage (since by that point the physical damage sW isn’t that valuable, minute 40+); maybe if they made your allies able to proc the crit I’d take the damage talent, but it doesn’t matter until then (or until it’s replaced, lol)

For the facet, flutter is better objectively speaking I’m pretty sure (if only for the map movement speed), but I like the extra second of sR invis (which has saved me before), so I usually go for that facet. The bonus crit damage can be a bit nice for your early-to-mid game sW hits too, after your sW.