All of the ADC changes and what they mean.
ADC's (In general): a little less starting armor, WAY less HP regain, More base HP, more HP per level
- Mages/AP damage dealers may have a harder time bursting squishy champions in the game
- Assassins/AD champs who can kill them easier, ESPECIALLY in the early game
- ADC's can take slightly more poke overall, but will recover from it much slower (unless it's AD damage poke)
Stormrazor: Total Cost: 3400g +65 Attack Damage +25% Attack Speed UNIQUE Passive: If you haven't attacked in the last 2.5 seconds, your next basic attack will critically strike. UNIQUE Passive: When you critically strike, gain 25% attack speed and 8% movement speed for 1.5 seconds.
- Effective in laning phase for specific carries, but I doubt it will be built as a first or even second Item for anyone who isn't
- Maybe an effective late game item for ADC's who are willing to sacrifice life steal/tank killing for pure AD, Crit, and attack speed late game. (example build being Stormrazor
two 
items, boots, and one additional item of choice. - AD assassins/ Fighters have a crit item that they don't need to build crit to use effectively. (
etc...)
Armor Penetration changed from [35% bonus] to [10% total]
New Recipe: [Last Whisper + Pickaxe + 625 gold]
Total cost increased from 2600 to 2800
Attack Damage lowered from 50 to 40
Armor Penetration changed from [35% bonus armor penetration] to [35% total armor penetration]
Giant Slayer passive removed.
Gold cost increased from 2600 to 2800
Attack Damage lowered from 50 to 40
Armor Penetration changed from [35% bonus armor penetration] to [25% total armor penetration]
- Indirect buff to HP based tanks/fighters due to giant slayers removal
- Last whisper is now a item for any AD champ who needs to face a tank or a fighter who's stacking armor, not just ADC's
- ADC's with this item will be doing more damage to all targets (Could be wrong, not sure how much that 10 less AD will effect ADC's facing squishier targets)
- Last whisper alone is overall less effective against tank champions who stack armor early, but more effective or as effective against anything else.
Costs 100 more gold, Combine cost on all corresponding items costs an additional 100 gold
- Just a flat nerf, it'll take longer to get Zeal/its items
New Recipe: [B.F. Sword + B.F. Sword + 1100 gold]
Total Cost: 3700g
Attack Damage increased from 70 to 80
[Removed] No longer increases critical strike damage.
[Removed] No longer grants critical strike chance (on its own)
[New Effect] UNIQUE Passive: Doubles your critical strike chance.
[New Effect] UNIQUE Passive: 20% of critical strike damage is converted to true damage.
- Now a more viable anti-tank/damage option for champions who can crit without building crit (
etc...) - Nerf to champions who don't commit to crit builds
- Buff to damage against Armor/MR tanks, Nerfed damage to anything else
- I've seen most people come to the conclusion that unless you have more than 125 armor, it'll do less damage (
at level 18 has the most armor in the game at 115) - Life steal less effective (doesn't apply to true damage)
- Nerf to ADC's early game, slight buff mid game
- They won't gain any additional crit from this item until it's done, where as before they could purchase
to get more crit chance. But when it is finished they gain 60% crit chance instead of 50%
New Recipe: [B.F. Sword + Caulfield’s Warhammer + 800 gold]
Total Cost: 3200g
Cooldown Reduction increased from 10% to 20%
[Removed] No longer grants critical strike chance
[Removed] No longer grants additional CDR based on critical strike chance.
[Changed Effect] Mana refund reworked: Now grants 1% of missing mana on hit.
[New Effect] UNIQUE Passive: After you cast your ultimate, your next basic attack within 10 seconds grants you Essence Flare for 8 seconds (30 second cooldown). Essence Flare: Gain 30% attack speed, and basic attacks refund 20% of your remaining non-ultimate cooldowns."
- Buffed/Viable item for AD fighters/Casters/Assassins
- No longer reruired to build Crit chance to gain full effects
- Nerf to mid/late game mana sustain
- Essence flair balance/goal is up in the air
Cost 200 less gold
- Flat buff
- Counteracts the zeal nerfs, more survivability in life steal in exchange for damage (crit) in the early/mid game
AD increased from 50 to 60
MR increased from 45 to 50
Shield value changed from [300 + 100% of bonus magic resistance] to [350]
- Less Niche
- Base stat buffs
- Slight buff to any champions who can viably build it
- Slight nerf to champions who don't stack MR
New Recipe: [B.F. Sword + Chain Vest + Stopwatch + 100 gold]
Total Cost: 2800g
AD increased from 40 to 45
Armor increased from 30 to 40
- Base stat buffs
- Slight buff to any champions who can viably build it
- Easier to build
Hail of blades
- Slight buff to ADC's in the early/mid game.
and of course ...maybe 
too. - Offers a more stompy early game rune for champions who don't want Lethal tempo
- Buff to Assassins/Divers who can rely on auto attacks
etc - Offers follow up damage after initial burst
OVERALL
- HUGE Buff to assassin Itemization
- Buff to AD fighter Itemization
- Huge Nerf to Armor based tanks
- Nerf to MR based tanks.... all one of them
- More importance on ADC Item builds
- Can no longer viably build Crit and On hit, Now needs to choose one or the other, Crit, Lifesteal, On hit, Tank shred, defensive)
- Slight nerf to ADC damage to champions in the early/mid game
- Takes longer to get items, Items are more reliable when finished rather than mid-build, no more bonus crit damage on IE, etc....
TL:DR Belive it or not, ADC's are getting nerfed, and assassins are getting buffed, fighters are getting buffed, and tanks are getting nerfed. It's not an "secret buff" or whatever.
Tell me if I missed anything in the comments
