Just you wait for Greven's response on this. God have mercy on thy soul...
When we say knight, TANK class comes out from my mind and not just a tank but the BEST TANK class since it wears the heaviest armor and the only class using shield in the game. Unfortunately, knight is the worst tank class in this game.
Comparing Knight and Warrior in tanking, they almost evenly matched. Beastmaster and Knight, with the OP hp and heal of a beastmaster, what can a knight say?
Lastly, comparing a Knight with a Monk in tanking, is a monk a tank class to begin with? wearing cloth like armor and knuckles can tank better than a knight? The answer is YES, with the skills given to a monk like Iron Skin defense +50% (passive), Steel Body health +35%, and defense +200% (buff) not to mention Protection Ki.
So, what is the knight's tanking skills? Aura Armor damage received reduced by 5%, +20% HP (which warriors have it too), Aura Shield reduce damage taken by 20% for 10 seconds. Lastly, Shield Fortress reduce damage taken by party with in 20m for 10% in 10 seconds. What I'm trying to say is, give a knight a BETTER TANK SKILLS.
Believe me, these are all in game experiences. I would love to post a video that a monk is tanking for our party in Dark Whisper. Unfortunately, I don't know how to take a video.
Ragnarok knows 4 different tank classes: Warriors, knights, monks and beastmasters. A tank can be determined by a special skill that raises the threat high enough to ensure that a boss focusses on that character. Every tanking class is meant to be unique, but none of them to be the best.
This creates choices and diversity, because otherwise you'd need only 3 classes: The best tank, the best DPS and the best support. So Ragnarok knows 4 tanks, 3 healing classes and 5 other classes. All of them focus on different aspects.
With exception of the Beastmaster, tank classes get two defensive skills. One with a 60sec starting cooldown and one with 120sec. The former can be used twice as often and therefore are only half as effective.
Knight - Aura Shield: 100% chance for 20% less damage
Warrior - Parrying: 40% chance for 50% less damage
Monk - Evasion: 20% chance for zero damage
So all three ought to reduce the overall damage by 20%. For a long time, the knight's version was the players' favorite.
The other four defensive skills are also meant to be similar effective.
Warrior - Endure: 40% damage reduction, can act
Monk - Ki-Protection: 50% damage reduction, can act (might require inner energy)
Knight - Shield Fortress: 50% damage reduction; can't act, but 20% damage reduction for the team (not 10%)
Beastmaster - Feral Defense: 100% damage reduction, can't act
A beastmaster would survive any damage, a knight can protect other comrades, whereas the monk and warrior stay mobile and can continue to attack. Favorites depend on the game situation. Due to the lack of true PvE with deadly boss AoEs, monks & warriors might now have the upper hand here.
But let's get on the most important part - the defense:
Both warriors and knights have the highest gear defense in the game. In fact every single osiris, himmelmez or cazar gear part grants twice as much defense (+100%) compared to beastmaster gear part and four times as much defense (+300%) when compared to monk. Both the beastmaster and monk have to spend skillpoints to compensate that. So they use 'magic' (f.e. to harden their skin) to achieve what warriors and knights get 'for free'.
Originally, the knight's shield alone increased the defense by ~40%, but WarpPortal changed that into a 10% damage reduction.
All in all, except for the BM, the tank classes can achieve 90% or more defense rate.
Beside the defense and the protective skills, you also have the healing skills. Yes, the beastmaster does have the most broken skills, but as long as you can have healer, heal pets or pots, this usually doesn't turn out to be that important to be a good tanker. The knight (as well as the warrior) can compensate that with a higher damage output, which reduces the time a bpss might damage/harm the team (see Eremis debuffs f.e.)