Don't knock it until you try it

Try what?

Say what you want about it, but after trying it out in a few games I wanted to talk about how strong this item actually is.

Yes, the stats are a lot lower than Magus. Runeglaive lost 40 AP and 10% CDR for its passive and 200 mana, so the passive that was added to this item needs to be really good, right? At first, this doesn't seem to be the case. AoE doesn't look too great, especially considering Runeglaive doesn't have the damage Lich Bane does (same AD ratio, lower AP ratio). But then you have the mana restoration portion of the passive, and this is where Runeglaive shines.

If you buy this item, then you have absolutely no mana problems when clearing the jungle. Don't buy this item? You can buy and all the mana and mana regeneration items you want, and you will still run out of mana if you don't have blue buff. Then you actually realize that you actually have enough mana to not just clear the jungle. You have enough mana to full clear the jungle, gank a lane or two, take Dragon, and still have enough mana left over to clear a camp or two before backing. And you still back with enough mana to punish an enemy jungler for trying to stop your back.

Health isn't guaranteed on some champions, but the health sustain from your jungle item's jungler passive and the clear speeds offered by Runeglaive's sheen proc and your champion's basic abilities give you enough health to actually gank above half health. Before, you could either gank with full health and no mana or gank with half health and half your mana pool.

Also, you can't compare Runeglaive and Magus without comparing the environment they create.

Now, since you don't have mana problems anymore, you can actually donate your mid lane blue buff. Before, AP champions needed to take their own blue buff in order to do anything around the map, especially if they bought Magus early. Being able to give your mid laner blue buff is huge for most, if not all, mana-using mid laners, especially when a lot of manaless mid laners are really strong or the enemy jungler can donate their own blue buff to their mana-hungry mid laners without gimping themselves.

Likewise, was the only option on a lot of AP champions because of their mana problems. Now that the mana problems are gone because of , you can buy whatever jungle item you want. Want ? You don't sacrifice vital mana regeneration for it unless you need it for your first couple clears. You might still want some health sustain, or you might want a little bit more mana in your early clears, so Ranger's Trailblazer would probably be ideal for quite a few champions, but Ranger's Trailblazer is not required like it was before.

Runeglaive didn't trade out 40 AP and 10% CDR from Magus for mana and an insane amount of mana regeneration. It traded that, AND it gave your mid laner blue buff and gave AP junglers more options with their jungle items.

TL;DR Runeglaive is a huge improvement over Magus because the mana sustain is strong enough that you can impact the map in ways that Magus didn't allow before.