Top lane tanks got screwed over, for the most part, because they finally nerfed the laning crutch that was Sunfire Cape. Now that the item is mainly a waveclear tool instead of giving you more power in champ-to-champ combat, the ability of tanks to lane got turned down. I even made a threat on it back when the tank update hit:
https://boards.na.leagueoflegends.com/en/c/gameplay-balance/bYuQIwXF-mstu-observations-on-top-lane-tanks
Since then, quite a few tanks got buffs:
got a minor rework, and looks fairly decent in the jungle - which was always more of his home than top lane.
, while not being a true tank, got buffed, as he was affected by the Sunfire nerfs.
's E got buffed with an increased Armor ratio. He is back at a winrate of about 51% on top lane.
's W got buffed to have a lower CD and a better HP ratio.
On PBE, there are also some more beneficial changes:
is buffed.
is buffed.
is changed to build out of Catalyst, giving lane tanks a really nice build path for that item. You'd think that tanks really ought to like Catalyst's passive - mana sustain through the damage they take, and health sustain based on their high mana costs.
is cheaper and accessible after a full jungle clear.
Also, I'd like to contest your assertion that tank items, overall, took heavy nerfs in the tank update:
got a goldneutral stat change and a positive passive change.
got a hefty nerf, I agree.
got improved for tanks (and gets even better on PBE).
and
were added - and while the former is somewhat underwhelming, the latter is a massive powerhouse.
got first buffed, but then nerfed as it was too strong.
got a goldneutral stat change, but the nerf that harshly affects its champ-to-champ prowess (and now awaits a cost reduction).
was buffed.
However, what really signifies the changes to be a buff to defensive itemization were the changes to Black Cleaver and the Last Whispers: While the combined HP/Resistance items were changed to have higher emphasis on the Resistance part, the ArPen of these items went down significantly (by roughly 20%).