So many champs have ridiculous health regen/healing (
) , but AP champs have no way of dealing with that untill 3000 gold. Why dont you give AP champs something equal to a 
which is only 800g, by just giving the Oblivion orb (1200g) Grievous wounds on top with the +15 magic pen, or reduce it to 10 magic pen if its seen as "too strong".
Nah mages don't need to be the best of everything
remove the health then, or the magic pen.
Mages should be able to 110 to 0 people in a matter of seconds, a few seconds worth of healing wont keep them alive
Im down but only take off the pen and make it only give ap and grievous wounds since then it gives a reason to build into morellonomicon.
Three reasons why this hasn’t and shouldn’t happen.
One - Many mages typically apply their damage at a much further range than other champions whether it’s through long range skillshots, damage over time abilities, or something similar. Liandry’s Torment itself greatly increases the duration, and thus the value, of the Grievous Wounds debuff. Luden’s Echo increases the ease by which the debuff is applied, particularly to multiple or elusive targets. By comparison, most AD champions cannot regularly apply physical damage outside of a typical marksman’s autoattack range, and several possess even lower range. Tanks require being autoattacked to apply Grievous Wounds for only a second, which is easily played around by many champions and only counters lifesteal during trades.
Two - Sustain is meant to counter poke but lose to all-ins. Most mages possess powerful poke tools, which their laning revolves around. Giving early access to constant Grievous Wounds removes this intended weakness.
Three - Most mages build Morellonomicon as a second or third item anyway, since flat pen is so strong and the item is more slot-efficient than Oblivion Orb. It probably is more gold-efficient too, but I’m too lazy to check. Anyway, this means that most mages will assuredly have Grievous Wounds at some point in the mid game, which follows Point Two by letting sustain counter poke during the lane phase while partially negating this single advantage as more damage items are built.
Its already a relatively cheap completion cost. And flat pen Ap and health already makes the item pretty gold efficient for 1600, just get the extra 1400 and finish it before starting your next item, if the enemy team has a lot of healing then it is worth delaying your next item to finish, and 
is a pretty reasonably priced item.
Edit: Also LOL at yasuo being included on your list, any sustain yas has early (before he builds 
) is ALL from runes, he literally has zero healing built into his kit.
No.
I don't like the idea of just giving everyone the ability to apply grievous wounds on a pretty easy component (imo this is also a problem with and 
, it feels like playing a healing champ in top lane comes down to whether or not the opponent remembers these items exist). I'd be more open to the idea of the old Morellonomicon passive on Oblivion Orb (i.e. apply GW only to targets below 35% health) (I'd also support this idea for and )
