Why do people purchase Morellonomicon?
Wiki says it's 100% gold efficient (starting items like 
have 200%) without the grieveous wounds passive. So wouldn't it be smarter to just buy 
for the magic pen and then move on to another item?
2 Comments
the GW is incredibly useful to have. You don't want to stop building up just because an item is 100% efficient without the other parts of the item's value. Having an item that's 100%+ gold efficient is preferable to stopping at 100%. Otherwise, why build Ardent during the censer meta? It was reaching 180% efficiency or some shit like that, WITHOUT the onhit passive everyone bought it for.
That being said, I could see an argument be made for stopping in the middle of building it because the champions Morello counters haven't reached the powerspikes that warrant its purchase yet
It's a great question. The answer is simply there are far more core items right now. For Example Malzahar right now really need rylais and liandry's to do damage. Rylais with cheap shot gives about 100 true damage per Malefic Visions, plus the slow, the HP and high AP, Liandry's gives a huge amount of extra damage given that AD champions have SO MUCH HP from items. Mana is sorted with a tear rush (which an go to Seraphs later for a nice chunk of AP, a shield, 20% CDR and never running out of mana again). At this point the game is probably over.
The simple fact is while morello's is a great item, it's no longer a priority for most AP champions, and while Oblivion orb is super effective, it's far better to look to build a full item that's strong rather then bits of items that are meh unless the enemy team have stacked healing champions at which point...well you're getting morellos lol.
It is really a situational item for the GW, much like a Zonyas against a Zed or Talon, or a banshee's against LB (such an underrated counter to her lol) rather then something that is as core as it used to be (when it gave mana sustain, CDR, AP and GW). Ludens etc are far more important now.