Welp, olaf got screwed this patch.
Olaf's whole design became very OP with S3. With a massive % atk speed passive, a attack damage passive based on his HP, and innate armor pen AS WELL AS immunity to CC, olaf was really OP in higher tiers of gameplay, so Riot basically slapped him with the eve treatment and said
"Well, we know that olaf's kit is OP now, so we'll just make him so bad no one will play him, then settle down to deal with him later."
But by how much did Olaf get screwed?
Tthe big list is right here.
-  Undertow:
- Slow now fades over the duration
-  Vicious Strikes:
- Cooldown increased to 16 seconds from 12
-  Ragnarok:
- No longer passively grants bonus armor penetration
- Now only grants bonus armor penetration while active
Let's take this nice, and slow.
Undertow, olaf's bread and butter. Let's him lane against zoning champs like teemo/jayce by giving him a bit of ranged damage for last hitting, and is what allows him to chase down champs with movespeed buffs. The key thing to note here is that it says "over the duration", which is basically another way of saying "we're cutting down this slow in half.
Now, it's not as bad as it seems, since olaf has the ability to reduce the cooldown of this skil by 6 seconds if he picks it up. However, this implies that the enemy is in a straight line with the axe path... a smart enemy will move slightly to the side, making the olaf choose between picking up the axe... or chasing down the enemy, which pretty much everyone did anyways.
It's not really a problem if you know how to throw skillshots, so I'm gonna give this nerf a 10 points out of a hundred.
Vicious strikes: Cooldown increased to 16 seconds from 12. This is a huge problem, because a large part of olaf's gameplay was sustain with respect to the laning phase. You take a ton of damage in a trade, or getting poked a lot? No problem, grab a dorans/vamp scepter hit W, and auto the minions.
Now, the time that it's up has been nerfed by a whopping 33%. Let's say over a 1 minute period you used to be able to activate Vicious Strikes a total of 5 times. Let's say... one auto every min, for 100 attack, just throwing out numbers here. at 12% lifesteal, that's 12 hp every attack for 30 attacks, every minute, which is about 360 hp a minute, under perfect conditions.
Now, you can only activate it three and a half times, which is barely 21 attacks! That's like... 252 hp! Bam, a fricking 30% nerf right there. And I'm not even counting the spell vamp from Reckless Swing and Undertow, or talking about the attack damage buff. WTF!
This is obviously a huge nerf, so i'm just gonna toss it under -50 points, out of a hundred. If this was a fricking test I'd be failing already.
This is important, important important. Before, a popular build would be to max Undertow first and build armor pen in your runes and masteries for a true damage ranged attack with 100% bonus AD ratio, or close enough. Just one or two of these bad boys would swing the lane in your favor. Without the passive armor pen from Undertow, you can't do that anymore, you actually have to build damage to get damage. -20 nerf points.
This is fine, but in conjunction with all the other nerfs, all at once? I just can't deal with it.
Riot, what are you doing.
-80/100 nerf points.