Like the Haunting Guise and Phage, the Hexdrinker and Seeker Armguard need more build paths, the enemy can predict your next item always that you have one of these items.
Edit: Phage have now Brutalizer, add now the Brutalizer instead.
I think that those items are only there as means to upgrade into their respective items, and are strong enough as it is that they don't need a new path. The weakest of the items you listed probably is the Seeker's Armguard, only because it's passive doesn't carry over, so that one might have a purpose (give mages a little help vs AD Assassins). As for the rest of them, their early passives are very strong. The cheap Magic Pen. on Haunting Guise is extremely vital to AP Assassins. The Hexdrinker's passive is ludicrously strong for AD Assassins or Bruisers that fall behind to an AP champion. Phage is freaking Phage (Jax will forever stick to you until one of you die, and that would be you who will die).
We need more items.
They should combine together into a hybrid dmg/hybrid def item. Muahahahaaa!
I need a new armor caster item badly ;_; i don' t always pick zhonya but i feel crippled if i don' t pick it all the times,a nd there are few other choices...
However there are worse offenders: mage and assassin/bruiser itemization is broad enough, and i belive tanky damage items and carry ones take bigger priority.
Like making phage build in a item that help less mobile carries ( with more ad than current) and haunting guise evolving in a les CC-dependant item.
I'm all for diverse build paths, 
this thing too.
needs a new build path. Everyone knows it's going to be updated into 
.
i cant see why you would ever want to build anything aside from a Zhonya's hourglass out of a seekers. It's an absurdly good item.
hexdrinker is intentionally inefficient because of it's early game strength, i believe.
...Why would you ever want a different build path from hexdrinker? It's entire use is to help you survive some magic burst while doing damage, and it's upgrade improves both aspects. There really isn't any other upgrade to hexdrinker you'd want (unless you want cdr/armor pen...but let's not give those with massive AD and a shield)
There's nothing wrong with Hexdrinker/ Armguard's build path, in fact they're ideal. 2 cheap component items into a reasonable combine cost. Your complaint is that it telegraphs your build? Kind of a non- issue. If you're going against a Zed, and you're an AP champ, chances are you'll get Hourglass as a 1st or 2nd item. As for Hexdrinker, it doesn't matter whether your opponent knows you're building it anyways; Hexdrinker counters you, you don't counter Hexdrinker.
+ 
= Armor+MR, some AP, and the debuff removing active for an item tanks can get.
Why would you upgrade your drinker again? Why would you upgrade your haunting guise?
Just saying, there's no reason to upgrade it until last item most of the time, it does its job fantastically on its own.
Also, it generally doesn't matter that people can predict your Zhonyas purchase. There's not a damn thing they can do about it once you complete it, it's not like you can counter build a zhonyas with some kind of "you don't get the zhonya active" item.
As for phage... i mean it would be great if it built into fromal for the purpose of fromal, but apart from that it really doesnt matter much.
I want seekers to have the passive that hexdrinker has.
Hexdrinker and the Maw is made to prevent bursting to 0 health by nukers, and I don't think there is an 'alternative' to that.
Also armguard builds into Moonfair Spellblade. why exactly isn't it allowed in SR?
Hexdrinker/Maw are probably the most well-designed items in the game. Plus, for almost any champion that can utilize the Hexdrinker, Maw is the perfect upgrade. Riot ought not to fuck with them.
Being able to predict the next item someone will build is not that big of a deal, really.
You say that like there's counterplay to items that aren't even finished.
Honestly I think the whole item system needs an overhaul. There should be a standard of low tier items for each stat, similar to how it is now. Then those low tier items should combine for possible scenarios. Ex: low tier simply AP item + low tier mana regen item = mid tier AP and mana regen item, slightly stronger than both of the ingredients. Obviously the higher tier items would have unique effects, things like %health, slows on-hit etc. but this would allow items to be chosen based on situations and individual games rather than "I'm playing champion X so I have to build these items or I'm not viable".
"Strategic Diversity"
need another final path too.
What could they possibly do to Hexdrinker as another upgrade?
Well Phage recently have a new build path that ends in Black Cleaver so maybe Hexdrinker and Seeker Armguard receive some variety in a near future
Imagine if they could be combined tho.
Add Brutalizer to the list please!
Haunting guise need more items too.
Scapegoat's Mask
Recipe: 
Aether Wisp + 
Haunting Guise + 265 Gold = 2600 Gold
60 Ability Power 200 Health 6% Movement Speed
UNIQUE PASSIVE – EYES OF PAIN: +15 magic penetration
UNIQUE Active: Creates a clone of a target allied champion that lasts 6 seconds (90 seconds cooldown). You can control the clone's movement with this item, but it deals no damage.
My dream is that one day, Moonflair Spellblade will return to SR in its current form (maybe toned down a bit). Diana would instantly become viable.
