"Rammus needs too much work for a class update"

At level 9, if you level W first, Rammus has ~62 base armor. Including extra armor from runes and masteries, he only needs one item to hit 140. Yes, MR will take longer to get that (as a side note, MR is getting buffs in this update - there is more of it available, and crap items (Banshee's Veil) are actually becoming useful (Abyssal Scepter gives MR and increases you and your allies' magic damage?!?!)), but tanks who can defend against any damage type just by virtue of their kit are generally unhealthy.

With these changes, Rammus can get massive amounts of Armor and MR, but he can't just immediately become unkillable to both physical and magic damage - he has to choose which one he needs to defend against first. All this does is shift his power from midgame to late game, and gives him even more power there.

Q's movespeed boost is worthless because movement speed has both soft and hard caps. What is worth something is the fact that it lost a second of duration at all levels, meaning Rammus has less time to get around, covers less space, and also deals less damage!

No, there is no hard cap for movement speed. There is a soft cap, yes, but that begins at 415 movement speed, so his current Q is affected by the cap just as much. With the soft cap (no boots or speed modifiers) Rammus' current Q maxes at 490 movement speed. However, at level 18, the new Q will max at 623 movement speed. At level 9, the new Q will max at 548 movement speed. Because of the acceleration, he will go farther with the new Q once midgame hits, even though it is 1 second shorter.

Ooooh, R does more structure damage after getting its actual damage nerfed. I'm sure that will compensate for everything.

One of the biggest issues with tanks recently has been how much reliable damage they can do. The midseason update, and these Rammus changes to an extent, are trying to change that. Rammus is getting better tanking potential and increased utility in exchange for damage. He's a tank. He isn't supposed to go around murdering everyone.

Not to mention, objectives are the main goal in League - you're supposed to destroy towers and, eventually, the Nexus. Bonus damage to structures is a big deal.

Yeah, it's worse early and better late. Also the damage from the thorns has been nerfed quite a bit - he would need 700 armor at lv 18 to equal the live damage at skill rank 5, lv 11. Also he slows himself now while using it.

The thorns damage is equal at 300 armor (current: W gives 120 additional armor for 420 total, Damage = 65 + 42 (10%) = 107 damage; new: W gives 230 additional armor for 530 total, Damage (lvl 18) = 20 + 53 (10%) = 73 x 1.5 = 109.5 damage). His passive deals 150% damage during W. I do agree that the slow is probably too high, and should at least be lowered to maybe 20-30%, if they have to keep it.

Q is an interruptible channel now, and got a 40% damage nerf, as well as a halved slow duration.

The slow amount was also doubled, and its hitbox and collision detection were cleaned up.

But the damage to champions isn't just down, it's WAY WAY down. Down by over a third. That is not something to just dismiss, given it's his Ultimate.

And he also gets a stacking slow on his ult, up to 64/80/96%, which is nothing to dismiss, either.

Except the parts which are pretty significant nerfs, the main problem being that he won't deal anywhere near enough damage.

He is losing upfront damage for more utility and pretty significantly higher tanking potential late game. There are tanks like Sejuani and Sion that are meant to be able to deal massive damage in certain situations, but Rammus is really meant to be a more tanky tank.

There are issues - the 60% self slow seems way too high, especially after trying it on PBE, and the attack speed buff during his taunt seems... out of place. I'm not really sure why he wants an attack speed boost, especially when his W will slow him too much to make use of it after the taunt has ended. The lowered Q, passive, and thorns damage in the early game is also a bit worrying for his early clears, but they can probably fix that with a "X% bonus damage to monsters" on his passive if it's an issue.

pardon?

That's why he has a taunt, the initial slow on his Q, and the stacking slow on his ult - which can stack up to 64/80/96%. 60% may well be too much for his self-slow, still, and I wouldn't be surprised if they changed it (remember, this is the PBE, things change).

At 300 Armor, Rammus' current W boosts him to 420 armor and deals 107 damage per hit. His new W boosts his Armor to 530 and deals 109 damage per hit.

Hexdrinker means they'll take 66 damage per hit, just from your W. However, you only take 16% damage during that time. They would need to be doing over 400 damage per auto to out-damage you (assuming they don't have Last Whisper/Black Cleaver/Lethality, of course).