Due to the Sky Island patch completely overhauling the crit rate formula, Valkyrie can pretty much run full power. There are some exceptions to this where you might run a little higher crit factor but the only thing you would need to switch out is green jewelry crystals at most. If you have doubts or don't know you should check your Shinra logs. You want around 70% Leaping Slash crit rate and 90%+ Twilight Waltz crit rate and then you are good to go.
Valkyries will still run as much power as they can; however, it isn't as omnipotent of a stat as it used to be. (This is actually a good thing since this means we will have less of a diminishing return on power in Ragnarok and Godsfall.) That being said, power is still very important.
In the current meta, Physical Amplification is the main stat we will be building. Valkyrie's core skills do high physical based damage and Valkyrie's passive gives a proportionate amount of magical amplification based on our physical amplification to help with our filler skills while slightly increasing all of our core skills other than Shining Crescent as well. On top of this, magic amplification gives added effects to our existing skills. For example, at 100,000 physical amplification, we gain 50,000 magical amplification passively. This adds 10% damage to Runeburst per Dreamblaze stack, 5% more on Gungnir's Bite effect (to total as 15% skill damage increase), and 5 more power to both Godsfall and Ragnarok.
Due to the removal of weapon crystals, crit power is the most important stat we can build on our gear. Unfortunately, the only normal crit power lines we can get are extremely low to the point where only nostrum's 1.42 and dragon proc's 2.0 and 1.5 are viable. However, there are 2 other forms of crit power: physical and magical.
At 100,000 physical amplification, the BiS gear would be three 0.06 physical crit power rolls on weapon, three 0.04 physical crit power rolls on gloves, and an innerwear with 0.14 physical crit power. Added together with the base physical crit power of 2.0, you get a sum of 2.44 physical crit power. (Magical crit power isn't great for valks.)
Power: Simply put, it increases the base damage you do. The more power you have, the harder skills will hit in both white damage and critical damage.
Crit Factor: Increases the chance of performing a critical hit.
Normal Crit Power: Increases the damage of your critical hits.
Physical and Magical Amplification: Simply put, increases the damage skills do based on their physical and magical modifiers. The amplification you have will scale with each skills respective modifier.
Physical and Magical Crit Power: Increases the damage of your critical hits through physical and magical amplification respectively.
Shred: Refers to flat reduction of target's special defense. This is shared and originates from Tanks and Healers.
Pierce: A percentage reduction of target's special defense. Pierce caps at 80% and does not affect damage if target's special defense is 0 or lower.
Ignore: A flat reduction of target's special defense. This stat can go in the negatives and increase damage further.
Damage to and Damage Reduction from Monsters: A flat increase and decrease of damage to all things pve. May have additional damage if you meet certain requirements such as attacking from the front, side, back or enraged monsters. May have additional damage reduction if you meet certain requirements such as having the highest amount of aggro, getting attacked from the front, getting attacked while monster is enraged.
Endurance: Simply put, it increases the base defense you have. The more defense you have, the less damage you take from enemies.
Physical and Magical Resistance: Simply put, increasing the either physical or magical resistances help you to take less damage from certain attacks. Some skills are directly affected by this stat.
HP: Your standard Health Point system. Some attacks are based off HP. If it reaches 0, you die.
Mana: The standard resource to use skills.
Attack Speed: Simply put, increasing this value increases your attack speed of all skills except those that are specified to not be affected by attack speed.
Movement Speed: Increasing this value affects how fast you can walk or run both in and out of combat.
Crit Resist: Simply put, increasing this decreases your chance to get receive critical hits, although some attacks are guaranteed to crit regardless of this number.
Stun Duration Reduction: Decreases the time you spend in a stunned state.
PvP Attack and Defense: A unique stat for pvp. Increasing the factor either increases or decreases damage to and from players respectively.
Impact: An irrelevant stat that is supposed to increase knockdown chance to enemies.
Balance: An irrelevant stat that is supposed to decrease your probability of getting knocked down.
Healing: Increases base heal of skills that heal specified numbers.
Stacking a stat over the optimal level is called a diminishing return and all stats have them.
Diminishing Returns: the point in which building more of a certain stat is less valuable than another.