Well, personally there isn't much to say on the items. They seem balanced to me. Maybe some items could be pretty OP with some heroes e.g buriza with void, aghanim with doom, blademail with legion commander etc... but overall they are all good.
With Magic Stick and especially Magic Wand it's not so much a question of which hero is buying it, but rather what laning situation that hero is in. Magic Stick and Magic Wand are good choises when facing off against enemy heroes that cast lots of spells in lane. Alternatively if you think you're going to be in a lot of fighting in the early to mid portions of the game buying a Magic Stick and upgrading it into a Magic Wand can be pretty benificial.
So if you really want a rule to say which heroes should and should not buy it, supports and heroes that are in the middle of the fight generally benefit the most. But I'd say you'd be pretty stupid not to buy it quickly on a hard carry if that carry's facing off against an enemy Bristleback, Zeus and Skywrath Mage tri-laning for whatever reason. The same logic applies the other way around. If you intend not to fight much early game (generally that is if your team has the stronger late game and weaker early game), and/or if you face off against a solo Sniper in lane, probably you don't even want to bother with a Magic Stick on a support.
I sell my Stick/Wand when I have no inventory slots left and have the money to buy a more powerful item to replace it with. Sometimes I keep it for the entire duration of the match as I find myself supporting a lot.
I just played lion and realized how strong he is now. Don't you guys think Lion's aghanims is too imba? I mean AoE 1025 damage every 20 seconds. Team me up with a good magnus and I bet we could own a team of 5 with that imba shit.
I think there are other good items to consider before aghs on a hero like Lion. If the enemy got lots of magic immunity or has the ability to get the jump on Lion and kill him before he can get a good aghs ulti off then you can probably get more value out of an item like ghost scepter, force staff or euls scepter. Consider mekanism and other items that can help your team and especially your carry to survive a team fight. Maybe you need a bracer to be effective without feeding in the early game. If none of your teammates are building drums then build your bracer into drums. The reasoning for not building costly items like aghs if you're supporting is that you have to be able to help your team survive throughout the mid game. Let's say you're playing against a pushing lineup for example. If you have the support role with Lion and rush aghs at the same time, if the enemy team is smart they will exploit the fact that your team is weak mid game and they will push down all the towers and potentially take barracks before you have your aghs finished on Lion. You have had low impact on the game because you couldn't really fight as well with blank point booster + ogre club on Lion in comparison to if you'd have had force staff or mekanism or a shitload of wards, detection and smokes.
If your Lion player is clearly better than everybody else and is continously getting kills without dying, then aghanims becomes a lot more interesting. You have to be able to farm into the item without loosing too much impact on the game. If Lion is considered a farmer and a carry on your team, then sure, aghanims might be really good in certain situations. But that is true for most aghs upgrades. Maybe you have a competent Magnus ally like you suggested. Maybe your team can hold the enemy carries back from farming BKBs before you have your aghs on Lion.
I also believe that the game is mostly balanced in regards to the pro scene. Maybe aghs Lion works wonders for some players in public matchmaking, but no pros are picking Lion (and if they pick him maybe they never build aghs on him) in competetive. Then icefrog or whoever's balancing the game would be more inclined towards buffing Lion and his aghs upgrade rather than nerfing them. At least I think that's how it works.
you'll most likely see a lion buying a ghost scepter against dps than crimsons though. but i do agree that zeus is a better aghs guy than lion. zeus surely hits 5 people where lion can only hit 3 or more people when they are clumped up.
Yeah, Crimson Guard is the new item. It's effective against attack damage though, not spell damage. It can more or less be thought of as a Pipe of Insight but for blocking physical damage instead of magical damage. It's useful in situations when the enemy team's damage is coming from right click attacks rather than from spells.