Entropy is a very nice item that perfectly suit champions that need lots of AD but lack CC or when you need to build a little tanky while prioritizing AD.

Kitae's however seems to share similar problems with Madred's and doesn't usually make it into on-hit builds, unless it's a very late game decision.

Consider it a subjective, unprofessional and very amateurish comment.

When I used to play more Dominion, I got Entropy pretty frequently on bruiser champions who had good AD ratios, like Lee Sin or Jarvan IV. I like the on demand slow, and it has a nice mix of defensive and offensive stats. It's actually something I would build on SR if it were available there.

I don't play much Dominion anymore, but it is a relatively frequent buy for me on Proving Grounds.

hardly ever buy entropy i would always build mallet or trinity in it's place.
I can't remember the last time i built a kitae's

Personally I never built an Entropy. It an item that falls between Frozen Mallet and Trinty Force. If you want the control you build Mallet, if you want damage you build TF. There just isn't a roll for it. I even like activation items (Omen, DFG, ect) but Entropy feels meh.

Kitae's I have built - on Kog Maw. That's it.

It's been thrown around that Kitae's should be an upgrade of Malady. I fully support that. I build Malady on a couple different characters.

Sometimes I get those items but I think they are suboptimal. I got Kitae's once on Lee Sin because the enemy was stacking armor, but a LW would have been a better choice.

So I think it's fairly clear at this point that both these items need looking at... kitae's in particular.
I think after S3 hits, I'll give them a balance pass. I don't have any plans on bringing Blade of the Ruined King over to Dominion currently, as it seems to very heavily favor bruisers. It shouldn't be too hard to give kitae's a few bumps.

The question you should ask is: "What role should these items fill?"

Do you want them to be niche-items good on just a few champions, or "standard" items that can be built by many champions? Entropy could be remade into an item for AD carries that want some slow. In that case, you might want to consider removing the true damage over time, since it doesn't really mesh well with most AD carries' kit. On the other hand, Entropy could be made as a bruiser item for bruisers than don't quite want Frozen Mallet but do want some slow, hp and damage. In that case, having true damage might not be so bad.

KItae's Bloodrazor could be made as a niche on-hit item that's good for a few champions, such as Warwick. Or it could be made as an alternative for AD carries that want to deal with people stacking hp. The latter, however, might be hard to balance. Due to the way crit works, passive on-hit effects usually won't benefit AD carries all that much. Furthermore, the passive being magic damage won't help most AD carries, since they tend to get armor pen. You could consider giving it physical damage instead of magic damage, or perhaps even true damage. True damage might be hard to balance, though. You could add an mechanic similiar to Vayne's Silver Bolts, but that might make Vayne feel less special, and the item might be problematic when Vayne buys it.

Due to all these factors, I think Kitae's should probably be used as a niche-item used for champions that want an on-hit effect that deals magic damage. Perhaps you could reduce or remove the AD and instead give it some magic pen? This, however, might make it a bit too similar to Malady. I'm not really sure what to do about it.

I don't think Kitae's should be given physical damage. The standard triangle of IE/PD/LW has already been shown to be a far more effective way of tearing through health than a Razor analogue ever will for AD carries against higher and lower health targets. Kitae's repurposed as an item for on-hit magic damage builds would probably be the cleanest solution, and the simplest change would likely to be just to remove the pickaxe and any AD from the recipe in order to make it less wasteful for those on-hit builds.

That being said on-hit builds are sorely lacking in lategame items, so having Kitae's build out of more stuff while providing more power would be nice as well.

Dominion casual here, I've only ever built Entropy once or twice, usually I never do because the characters I play that want it for the HP want more of it, and the characters that might want it for the AD want more synergistic stats instead of the active and HP. It's just a strange item with no clear optimization, I really never know the situation I'm supposed to build it in.

I've built Kitae's on Kog, that's it, though many times it feels like a PD/LW combo would be better anyway.

To be perfectly honest, isn't Kitae's a problem item for the exact same reasons as Madred's Bloodrazor is, in the way it only pretends to counter tanks and the like? Madred's is getting removed for being awkward and not fufilling its intended role from what I understand, shouldn't Kitae's fall under the same rework logic?

Entropy suffers from gold efficiency problems. The other AD caster items just have better combine effects. You're effectively getting a slow + 80 DPS on hit every 60 seconds. Compare that to crazy item efficiency (sanguine), the only way to scale armor pen (LW), or CDR (brutalizer) and it kinda falls short. IMO a cost adjustment will fix it. "Eh" effect for cheap might not be flashy, but it's often effective.

Kitae's just bites period. The same reasons Madred's is getting replaced apply still. Further, in terms of slot efficiency, its proc isn't horrendous amounts better than Wit's End's proc (better at 1700 HP) or Ionic Spark proc (better at 2400 if Ionic hits two people). It's "secondary" benefit is self-synergy (neither Wit's nor Ionic has self synergy with its non-AS stat), but it's already less efficient b/c it builds out of pickaxe. Furthermore, Wit's severely reduces the effectiveness of the flatpen build and Ionic scales much better in fights with 3 or 4 people (AND has a slightly better AS to boot).

And the kicker? You often don't build any of those three. You build Lightbringer because it's just way more efficient and gives unique utility.