Neverwinter has a unique and complex stat system. It isn't easy to understand and manage, but players don't need to deal too much with it during the leveling process. Once a player reaches the max level then need to start working on their numbers because characters with well balanced stats can be extremly powerful.
There are 15 Main Stats that affect your performance in the game. Their effectiveness is expressed by a percentage, which can go up to 90%.
Your TIL (Total Item Level) and Ratings are the main modifiers for your percentages. But there are also many things that give bonuses directly to your percentages (race, ability scores, boons, equipment and companion equip bonuses, food, buffs...).
Your Ratings cap at your TIL, so having more Rating than your TIL will not make you stronger. On the other hand, every 1000 points below your TIL in Ratings, will decrease your percentage by 1%. Percentages are rounded on your character sheet, but not for the actual damage/healing calculation.
You start the game with 5000 TIL, but 0 in your Ratings. That means that all of your percentages are at 45% from your Ratings. And you also have a bonus in one or many stats thanks to your Race.
Most of the items in the game give a total of 15 rating points per TIL, which means that the sum of your percentages (from Ratings) will not change when you equip better gear (only your Damage and HP will). Your percentage points will only be reattributed from the stats you don't focus on, to the ones you do. But that's unfortunately not true for all of the items. There are items that give less ratings per TIL (currently collars, guild boons, many utility enchantments, the mount combat power...), and these will decrease your percentages. Usually, more TIL is good. But with these items, it's not always the case, especially in Scaled Content. Only percent bonuses can make your percentages better overall.
Players and monsters/bosses have the same type of stats:
Offensive / Healing Stats
• Power - Contributes directly to higher damage or higher healing for healers. Monsters have 90% Power.
• Accuracy - Reduces the amount of damage the target can deflect. --Note that in NW one can't "Miss a target". Monsters have 90% Deflect Severity and 0% Accuracy.
• Combat Advantage - Determines the bonus damage when the player has combat advantage over their target. (Reduced by targets Awareness). Monsters have 90% Combat Advantage and 0% Awareness.
• Critical Strike - Determines the chance for a critical strike/heal. Monsters have 50% Critical Strike.
• Critical Severity - Determines the amount of bonus damage / healing for the critical strike/heal. (Reduced by targets Critical Avoidance). Monsters have 90% Critical Severity and 0% Critical Avoidance.
Power and Combat Advantage, as long as you surround your enemies, are as effective. They are much more important than the other stats. Neglecting them is very detrimental, and they also yield much better results than the others. You can put all of your points in them, until they are fully capped at 90%, without looking at the other stats. Combat Advantage is the reason why you should never use abilities that push monsters when you are playing in a group, and why positioning around monsters is very important.
Critical Stats and Accuracy yield poor results. They can be entirely neglected without huge drawbacks. Investing in them gets you better and better results (never as much as Power and Combat Advantage though). Critical Stats give better results than Accuracy, and to maximize their efficiency, Critical Strike should be equal to Critical Severity (it's not bad to have more points in one or the other, but for the same amount of points in Critical Stats, you get better results when they are equal). Accuracy should be the last offensive stat to focus on.
Defensive Stats
• Defense - Reduces incoming damage. Monsters have 50% Defense.
• Awareness - Reduces the enemy's bonus damage when they have combat advantage over the player. Monsters have 90% Combat Advantage and 0% Awareness.
• Critical Avoidance - Reduces the enemy's bonus damage from Critical Severity. Monsters have 90% Critical Severity and 0% Critical Avoidance.
• Deflect - The chance to deflect a hit. (note deflecting a hit reduces the damage by some amount, there is no a "miss", hits always connect). Monsters have 50% Deflect.
• Deflect Severity - Determines the amount of damage reduced if the hit is deflected (enemy's Accuracy reduces this reduction). Monsters have 90% Deflect Severity and 0% Accuracy.
Defense and Awareness are the stats nobody should ever neglect. While Defense gets lower and lower returns, Awareness gets better and better returns. And they cross at 45%. Past this point, Awareness becomes the most important defensive stat to focus on, especially because boss monsters always have Combat Advantage over you, and do not need to have another monster to surround you.
Critical Avoidance, while not the most important defensive stat still quite important to measure your resistance to being killed in a single hit (or a succession of unlucky critical hits). Nobody should neglect this stat, but it's not as important as Defense or Awareness.
Deflect stats can be neglected entirely with almost no drawbacks. They yield about as much as Critical Avoidance when focused on. It's much better to focus on Deflect before investing too much into Deflect Severity. The best returns are achieved when capping Deflect with 55% Deflect Severity, before investing more into Deflect Severity.
Other Stats
• Forte - Converts into a bonus to 3 other stats, depending on the paragon.
• Control Bonus - Increases the time a control effect affects a target. For example the length of a stun.
• Control Resist - Decreases the amount of time enemy's control effect works on the player.
• Incoming Healing - Increases the amount of health points recovered by skills (personal and external).
• Outgoing Healing - Increase the amount of healing the player can do to others.
"Brief" summary about the Stat System in Neverwinter. It is complex so there is an individual menu (on the left) to extend the information you find here
