@meddler: sheen and its items (except lichbane) hold bruiser itemization back.
let me explain.
as others pointed out before,
is probably the most bruiser specific item in the game, due to a lot of its power budget being tied to health and more importantly its base ad dependent scaling.
most squishier carries, and assassins have generally low base ad values and level scalings, while juggernauts have some of the highest base ad values in the game. this guarantees that steraks will be more stat effective on juggernauts and other beefy fighters than anybody else.
on top of that, most squishier carry classes that are geared towards stacking ad items have their kits centered around bonus ad scalings on their abilities and passives. steraks will never be as effective on
and other squishier carries as on juggernauts who have most of their abilities geared towards total ad scalings. which means that the base ad increase off the item doesnt factor into assassin, skirmisher or marksmen abilities and burst and makes it an undesirable item for them.
by using base ad increases and scalings, it would technically be possible to design an entire separate line of fighter items, independent of tank or carry itemization, with little risk of abuse cases by other classes (like the entire phase of brusier skirmishers and assassins). it would also make it possible to better balance fighters by their itemization independent of other classes, and individual fighters by their base stats.
for example if fighter items were designed after this model. a lower base ad scaling on divers compared to juggernauts would force divers to build slightly more into offense, and we wouldnt create situations were
becomes as tanky as 
the only thing that prevents us from doing this are these items.

the interaction with sheen passives and more base ad increasing items would create an absurd amount of burst especially by 
i think it might be a good idea to look into reworking the scaling of sheen items, to make room for more fighter specific items, and to rework some of the existing items to be more targeted at fighters by base ad increases.
one option would be to simply split
scaling into a lower base ad dependent component (like 50% base ad) + a level scaling component, so base ad increases dont interact as strongly with sheen.
some fighter items that could be changed to steraks model of base ad increases would be first and foremost

possibly 
and
damage component
but it would also be possible to add more fighter items based on this concept to the game.
+upgrades would be nice, so it would be a worthy component item for once)
This means base-ad scaleings can be kept fot it's original purpose: high basedamage abillities that aren't absurdly strong when first maxed but instead scale independant of abillity rank aswell.
And for the "a lower base ad scaling on divers compared to juggernauts would force divers to build slightly more into offense, and we wouldnt create situations were
and other assassiny type champions
would need to have his bleed and dunk reworked to utilize total ad scalings reasonably otherwise he would be guttered by such a new line of items that he wouldn't be able to properly utilize.
+