For sure, the Tank Update left tanks in a weak state of balance, but every major update in the past has generated balance upsets (the Assassin Update did the same thing when Lethality was initially undertuned), and tanks are likely to become stronger in the near future with targeted buffs to champions and items. What bothers me more is the direction of the update itself, which seems unclear even after release.
A lingering issue thus far in League has been that of the identity of tanks, and how they differentiate themselves from fighters. For years, there's been confusion between the two classes, due to how they share similar strengths (they're tanky, and generally have CC and mobility), weaknesses (they're usually short-ranged and thereby kiteable) and playstyles (both often start out in the jungle or top lane and migrate to join their teams after the laning phase, standing in the front line and brawling whenever an opportunity comes up). Unlike every other class in the game, each of which is completely unique in how they play and contribute, it's not easy to draw a definite line between most tanks and fighters, and so the Tank Update was a prime opportunity to fix this: the intention of toning down tank damage was especially good, as it would establish a clear distinction between tanks, who'd trade off damage for massive amounts of crowd control, debuffs or other forms of disruption that don't involve direct damage, and fighters, who'd have less CC in exchange for much better sustained and/or AoE damage.
In practice, though, none of the tank updates resolved this issue, and in fact made things worse: Maokai, a warden with moderate to low overall damage, became a hybrid vanguard/AP mage bot lane support, with a particular emphasis on damaging his opponents with his E; Sejuani, arguably known for being a more damage-heavy tank, was given single-target burst out of the blue; Zac, also a tank with above-average damage, received number nerfs, but was still left with a pure nuke on his kit. Effectively, many tanks still possess diver-esque kits with a spread of nukes, CC and self-protection across their abilities, which leaves every member of either class at risk of flipping denominations with just a few number tweaks, a la Rek'Sai.
The other issue is that of itemization: one big reason why there's so much overlap between tanks and fighters is because they still share much of the same item pool, with "tank" items making champions flat-out more durable, without synergizing much with any tank kit in particular. It's this generic power that has, time and again, caused those items to be used by the wrong champions in order to negate core weaknesses, e.g. tank Ekko, tanky Yasuo or bruiser Fizz. Additionally, the existence of Sunfire Cape as a core tank/bruiser item gives all tanks more damage than they likely should have. Beyond the addition of two niche items, the Tank Update did nothing to address these issues, with the shift from health to resists and the nerfs to Sunfire's damage simply making tanks weaker in the early game, with no tangible benefit to their mid or late game. Squishy damage champions are still at risk of building tanky, with bruiser Fizz builds reappearing immediately after the update, so it's likely the stat changes on tanky itemization did not achieve their core goals.
The TL;DR to this is that, while the Tank Update didn't exactly kill tanks, at least not in the long term, it doesn't seem to have succeeded in setting a strong foundation for vanguards, or any other kind of tank, in the future. Tanks still overlap heavily with fighters, perhaps even more so than before, tanky items can still be picked up by squishies, and several affected champions, such as Sejuani, Maokai, or Galio, have lost much of their original identity for no clear reason and become more homogeneous as a result, which is the complete opposite of what the update set out to do. Imo, this is perhaps one of the few updates that did more harm than good overall, and will have many more negative long-term consequences as a result. I hope Riot takes another look at their changes here, so that they may better reorient their design philosophy for tanks in the future, as we still haven't had a non-support tank get released since Zac in 2013.
u forgot him, the forgotten Champion also got hit
