When will Riot finally adress this item for real? From what I know you can't really balance it by touching the price, because unstacked its the least cost efficient item, but fully stacked it becomes more valuable than a fully stacked Mejai's in terms of stats.
Also the fact of how it interacts with Sated Devourer (3 AA full- stacking) and its raw power on a large number of champs is really making the game unfun to play. You go 5/0 against Irelia top? Worry not, once she gets to Tabi + Guinsoo's you can pack your bags and leave the game.
I could make a list of all the other champs but it doesn't really change anything if I do it, Riot will just continue to ignore shit like this and thunderlords being used literally on every position except for very few edge cases.