There are a few skills that you should really be careful of when thinking about whether to max a skill or leaving it at level 1 (or 0)
The following advice are in NO WAY telling you NOT to get these skills. They are written with the intention of making you think VERY carefully before spending your skill points because it costs REAL MONEY to reset your skill points if you make a mistake. You do NOT get a free skill reset when you change classes at level 25, so you should plan your skills/stats before you even start playing the game, unless you're willing to spend money later on to reset them.
Here's a skill calculator to play around with: http://ro2base.com/b...1.1.1/0.0.0.0.0 (Btw the cooldown of Shield Fortress on this should be 120 seconds, not 12 seconds)
Head Crush - This skill causes a bleed effect over 20 seconds. Edit: The bleed effect is refreshed every time you use Aura Strike on the target, so you only have to cast it once at the beginning of the battle. The % damage increase from investing more points is very little, as you can see from the calculator.
Provoke - From level 1 to level 5, this skill decreases your cooldown from 20 seconds to 8 seconds. 8 seconds is still quite a long time. If you've got enough damage with a STR/AGI or AGI/INT build + lv 5 Aura Armor, it's usually enough to hold aggro without casting this.
Mass Provoke - From level 1 to level 3, this skill decreases your cooldown from 180 seconds to 60 seconds. 60 seconds is still a VERY long cooldown. Most people hold aggro spamming Grand Cross, which is doing damage almost EVERY SECOND + Aura Armor. Think about whether you need points for this.
Battle Tactics - At level 2, it's an extra 0.4% damage on your critical hits. Most Knights reach around 150-200 INT by end-game from cards/gear/titles alone. At 150 INT, this equals 60% EXTRA damage on your critical hits. A requirement of this though is that you need to have decent crit. 20% critical rate can be achieved by getting roughly 200 AGI + end-game buffs - refer to comment #11 here: http://forums.playpa...battle-tactics/ There are AGI/INT builds that abuse this, the most extreme form is swallowing Maestro potions increasing INT by 112 for 30 seconds.
Concentration - At level 5, increases attack by 20% but increases damage received by 10%. Many people are put off by the +10% damage received so they don't invest in it, but +20% attack increase is pretty much the strongest attack buff that Knights can get. Increased attack = increased aggro generation. If you can hold yourself comfortably in your tanking, you can certainly consider this skill.
Aura Mastery - At level 3, 15% chance to not consume Aura when skills that normally consume Aura are used. That means 2 Aura Blades in a row or Concentration followed by Aura Strike straight after. Some say 15% chance is low, you be the judge.
Aura Heal - There's plenty of guides on this forum already that talk about the dismal amount that this skill heals you for, so I won't bother going into this.
Shield Charge - Increasing levels will only decrease cooldown. At level 5, it reduces cooldown to 20 seconds. For PVP it's still quite a long cooldown. Keep in mind it doesn't do damage. The usefulness is up to you to decide.
Shield Boomerang - From level 1 to level 5, increases damage from 18-27% with a 15 sec cooldown. This skill's used for its slow effect rather than its damage. The usefulness is up to you to decide but if you do want to use this extensively, pair it up with max Shield Boomerang Mastery for obvious reasons.
Shield Boomerang Mastery - As above.
Shield Bash - Similar to Shield Charge with a long 30 second cooldown and a little bit of damage and 2 Aura generated. Edit: Over a long period of time, throwing this skill whenever cooldown is up will increase DPS slightly, you're generating 2 Aura instead of 1 so you can cast 1 less Bash. The cooldown is the main drawback. The usefulness is up to you to decide.
Shield Cannon - Strongest Knight attack, but 30 second cooldown. The problem with this skill is the long animation, the damage without critical is about the same as an Aura Strike with critical. However, if this skill crits, it'll be much better than Aura Strike. The usefulness is up to you to decide.
Aura Shield and Shield Fortress - both have long cooldowns, but they're about the only active skills that can boost defense. If you plan on tanking, Shield Fortress is a must-take (yes I'm making an exception here)
Edit: Final Protip - Using a HP potioin to heal yourself will increase your aggro! If you find yourself in a crucial situation where you look like you might be losing aggro, use this to your advantage!
Edited by SolidJelly, 11 May 2013 - 10:33 PM.