Uncommon items for different uses that it is common

There are several items that I almost never see unless they are intended to be combined into a bigger item. What I wonder is if these items could be used for their intended reason and not just to complete a recipe.

Buckler, many know this item only as a component for Mekansm and never get it for other uses. However the item looks quite interesting, it gives +5 amror, boosts all stats by 2 points and gives an active that boosts armor of all friends in the aoe by 2, that means that for 10 mana you get +7 armor and the effect stacks with armor buffs of Mekansm and Ring of Basilius (and it's upgrades). My question stands if it worths to get this item just for the armor boost or if it worths to get another Buckler after completing Mekansm to get a lot more armor and be able to boost all your friendlies with +4 armor or even +6 if you already have Ring of Basilius.

The second item is Soul Booster, commonly used only for getting Bloodstone it combines all boosters into great health and mana boost while also adding regeneration for them. I wonder if it is worth getting the item without intending to build it into Bloodstone, just to get a lot extra mana and some health.

Last item is actually a complete item but I rarely see it, it's Rod of Atos. 50% slow is a good thing but the cost of the item as well as that it only boost intelligence and health but nothing else, thus it is not commonly built as core, and by the time you get it for postcore, the use of slow is little, these all make it a questinable choice. I mean it can only be used for chasing fleeing heroes after a teamfight but that is useless since the hero should not threaten you again alone, and in teamfights it could be used to slow dangerous melee heroes like Sven with God's Strength to practicly disable him, but Eul's Scepter of Divinity or a bit more expensive Scythe of Vyse would work a lot better. So I wonder, is it worth buying this item?

Buckler is a nice item for early game pushing, because it gives all nearby creeps a (practically) free 2 armor buff that, like you said, stacks with Ring of Basilius and its upgrades. For heroes that rely on summons to push early on, such as Nature's Prophet or Enigma, it's a decent option. If I'm building a Mekansm, I also like to get it before Headdress and hold onto it until Mek is complete. The main downside however is that it provides very little stats (other than armor) for its cost, as compared to items such as Bracer, Magic Wand, or Urn of Shadows. It also cannot be built into anything (besides the previously-stated Mekansm) and the armor buff is not nearly as noticeable late-game, so most heroes would just end up selling it as the game goes on.

Soul Booster is a very underrated item, in my opinion at least. It basically gives you all the benefits of the individual boosters, along with a free Void Stone and 2 Ring of Regens (about 1575 gold). If you know you can't keep many charges on Bloodstone, then sometimes a Soul Booster can be more cost-efficient. After all, combining it with a Perseverance only gives you 50 HP, 100% mana regen, and 5 HP/sec. which is arguably worse than the bonuses of Perseverance itself. However, the item itself is still rather expensive, so the heroes that would usually buy such an item (mostly support heroes) probably won't be able to afford it in most situations anyways.

And finally, Rod of Atos is a pretty decent item for tanky casters like Death Prophet, Necrolyte, and even Outworld Destroyer. But its cost, combined with the fact that its active is rather underwhelming, usually prevents it from seeing much play. Both Force Staff and Eul's Scepter of Divinity have good actives for a cheaper price, and like you said, the stats are mediocre at best.

As a support, I usually don't push, and as a pusher, I usually don't get Mechansm. I think 2 hp regen aura is better than 2 armor.

I think regen is better than max hp/mp so I usually get a Perserverance. In addition, a Perserverance can build into a Bloodstone, Refresher, Battlefury, or Linkens, so it is more flexible than the soul booster.

A slow is the least effective type of CC - the victim can still move and use skills.

So basicly what I was afraid of, getting those items for any other reason than to later get the upgrade is waste of money or very situational. And getting another Buckler after completing Mekansm to further boost armor of others is not that good idea either.

I'm kinda sad about Buckler. Maybe making the armor buff as another effect of Mekansm aura because the Buckler effect is practily lost as Mekansm has a lot longer cd as well as activating it just to boost armor will leave you without the heal later on.

About Rod of Atos, something tells me that making the effect aerial or making it need only one Staff of Wizardry, might make it more cost-effective. But I don't think that will ever happen.

Actually, Mekansm's active increases armor as well, 2 just like buckler.