The info below is a bit out of date as it refers to the beta. If you happen to be looking for an up-to-date reference for your Dragonknight, I suggest this manual. It includes some killer advice on leveling up, builds, skill rotation, and gold farming.
Dragonknights are well known to be one of the most powerful warriors here at Elder Scrolls Online. Although the solo gameplay of these warrior types can be fierce, Dragonknights can also be played well in a group. The Dragonknight class can be specially trained for a group or solo gameplay. To build your character to be fit for group gameplay, however, you must consider the race, the skill tree, and some gameplay strategies.
Health restoration and regeneration are important for your character when playing for group mode; you would be needed to increase your teammates’ strength and defenses without worrying too much on health. The suggested races for tanking build would be Nord, Khajiit, and Orc. They all have Robust for one of their natural race abilities. This specific ability allows them to regenerate their health by 5% while in combat.
The recommended eso dragonknight skill tree to follow would be the Earthen Heart. Many of the attacks may be long range, but you are also allowed to somehow disable and slow down your enemies. That way, you and your allies, especially the elder scrolls nightblade, would be able to work together as a team and take every single one of the enemies down.
The Stonefist and Molten Weapons skills under the Earthen Heart skill tree will both play important roles in gameplay strategy. Since Stonefist not only damages but also knocks out an enemy for a couple of seconds, you can use this attack on multiple enemies and give your teammates a chance to finish these enemies off. The Molten Weapons skill would be best used right before and throughout the entire battle. Using this and Stonefist in a group in this special manner is sure to help you and your team grow.
Another skill to unlock after Molten Weapon is Obsidian Shield. This skill should be used in the same way as the Molten Weapon skill. The final two attacks you can unlock are the Petrify and Ash Cloud skills. These are the two skills will that disable your enemies. It could probably depend on your enemy, but using these two skills interchangeably in some sort of pattern can also count for a good eso dragonknight guide. For example, you could use the Petrify skill first and use Stonefist on most if not all of the enemies. The enemies your teammates have not finished off that are fit to attack again can get hit by your Ash Cloud attack.
The info above is a bit out of date as it refers to the beta. If you happen to be looking for an up-to-date reference for your Dragonknight, I suggest this walkthrough . It includes some killer advice on leveling up, builds, skill rotation, and gold farming.