Precision is a tier 5 cunning mastery with 5 ranks.
Ferocity and Stormraider's buffed, Precision nerfed.
If you've played even a handful of games on patch 5.24, you probably learned the same thing we did - 8-10 Thunderlord's Decree per game is probably too many. Yet, no Thunderlord's changes. What gives?
While Thunderlord's Decree is the go-to mastery when you're looking to dominate your lane, we're leaving it as-is for a few reasons. First, we're looking to it as a 'goalpost' from which we balance the other keystones around. It's something you can easily play around, has a good amount of impact, and synergizes well with certain champion kits. Additionally, we're avoiding playing 'whack-a-mole' with the Keystones (ie: just nerfing whichever is best at any given moment). By recognizing TD's strength and matching others to it, we build a better ecosystem for Keystones where you're free to adapt your builds, rather than just playing champions that abuse the best mastery.
So how are we tipping the scales? Injecting some strength back into Ferocity's Keystones while reverting buffs to Precision should help balance things out, no matter how you seek to deal your damage. Toss in a pretty spicy update to Stormraider's Surge and you have a wealth of options at your disposal. It's still possible that Thunderlords is over-tuned after all this, but bringing the others more in line with the leader should help us gauge how big the discrepancy is, rather than just cutting down the top over and over again.
BASE ARMOR PENETRATION :  ⇒ 3
ARMOR PENETRATION PER LEVEL : [0.5] ⇒ 0.3
Armor penetration and Thunderlord’s ratio increased. New assassin mastery for assassins. Windspeaker’s blessing changed to flat from percentage scaling.
Cunning, on the other hand, isn’t pulling its weight when it comes to assassins. To help address their woes (especially the attack-damage ones), we’ve added or boosted damage from the tree across the board to enable the flashy, risky dives and outplays their known for. On the other side of the tree, Windspeaker’s was doing too much lifting toward making end-game tanks unkillable, so we’ve changed it to a flat amount. This makes it more effective on targets with low defensive stats, but less effective on the dude (or dudette) with 400 armor and MR.
ARMOR PENETRATION : [3 + 0.3 per level] ⇒ 5 + 0.5 per level
We're updating the mastery system to offer focused, high-impact choices rather than a slew of nuanced micro-math optimizations. Each tier of decisions now successively grows in importance, ending in your final 'keystone mastery' which fundamentally impacts how you play your champion.
No longer just 'Utility', Cunning is the tree for those living in the moment. Want extra speed for that clutch save on an ally? Perhaps you're looking to dive in and take out a low health target instead. Cunning's your go-to tree for both! Buyer beware: unlike Ferocity's offerings, Cunning's benefits are really only effective against softer targets, so think a lot about who you'll be fighting before spending your points!
ARMOR & MAGIC PENETRATION : 0.6/1.2/1.8/2.4/3 + 0.06/0.12/0.18/0.24/0.3 per level
TOTAL AT LEVEL 18 : 1.7/3.4/5.0/4.8/8.4