Why was the AD stacking item removed while the AP one stayed, got a buff, and a safer version you can pre-stack? AP champs rely more on burst, which is harder to counter, than AD champs (Aside from Assassins, but those exist for both types).
Serpents Embrace2 votesWhy was the AP spell vamp item removed but the AD one stayed?
If you take Mejai's you better take Death's Dance too.
General Esdeath 1 votesDeath's Dance isn't a stack item...and you mean lifesteal? You mean 
? Death's Dance literally just mixes these 2, with a DoT that saves you from burst for a few seconds, and is built on almost nobody.
Serpents Embrace1 votesWill of the Ancients was an AP counterpart to Death's Dance. The way Dance allows you to heal off all physical, Will healed off all magic. But, AD is supposed to be the long term DPS, sustaining off of hits is more suited to an AD playstyle and either neglible or oppressive on an AP with no in between. Will doesn't really belong but Dance does. You could argue that Gunblade now fills that niche but that'd be a dumb thing to say.
Similarly, AD isn't meant to have the best initial damage. Sure, some champions like Talon or Zed specialize in AD burst but their damage values are often smaller than an AP counterpart like LeBlanc because they have stronger follow up damage from auto attacks. AP champions can't rely on auto attacks to finish off disabled or weak targets, so giving them a larger attack stat coincides with having them focus on high initial damage. As such, Sword of the Occult doesn't belong but Mejai's does.
If you want to say remove Mejai's because there's no Sword of the Occult... the same logic applies to removing Dance because Will isn't around anymore. But AD and AP don't need to have perfect mirrors on what their items offer them, the game is kind of better for it.
General Esdeath 1 votesWill was bad because it didn't help burst champs as much as the ones with low CD's who gained health from skills. Death's Dance isn't good either and I wouldn't care if it was gone, but it doesn't present the problem like Mejai does with snowballing, which Riot says they don't like and try to remove via new bounty system.
Reikken2 votes[{quoted}](name=Serpents Embrace,realm=NA,application-id=3ErqAdtq,discussion-id=1lpZTTfE,comment-id=0001,timestamp=2016-08-15T04:52:17.457+0000)
Why was the AP spell vamp item removed but the AD one stayed?
because vampires aren't AD
Serpents Embrace1 votesYes, I'm aware of the abuse cases Will had. The question was rhetorical, referring to the underlying reasons why AD based champions gaining life based off of damage dealt isn't as problematic or how AD champions having easy access to high attack stats while snowballing was more problematic than when an AP champion does it.
lccarus1 votesPre-stack?
Malignant Vemira1 votes
Stacks transfer over into 
General Esdeath 1 votes^ plus it costs less, gives bonus healing from pots, and is a safer buy.
Erockandroll1 votesI think Riot wanted to make Stacking items better in general. But the AD item Just got left behind.
I think the reason for that is, AD scaling with Crit chance and Attack speed. Potentially, a otherwise pure tank, might take such an item as their only real AD item, ad Assassins would obviously combined it with Armor pen. But clearly those two classes would get shafted, if the ADC completely broke the AD stacking.
Yet balancing an AP item seemed easy enough, since raw AP is pretty ubiquitous over all classes that use it. As for the whole buff. I'm not entirely sure if the final item was a buff. But Riot did make the Barrier to entry extremely small by basing it off a starter item.
General Esdeath 1 votesYou could argue that AP plus CDR (old mejai) and move speed (current) also cause a problem. Kat, Annie, Veigar, and Fizz all benefit from the movespeed and cdr.