The current meta only consists out of zerging. As a solo player or small group you don't stand a chance in any situation. The game is build around zerging only and massive combat. The only way of beating another raid is by having a larger raid than the enemy or time all your abilities to go off at the same time.
Due to the focus of the game being on zerging and large raids, only high damage AOE abilities are viable to run. Any other abilites are rendered useless. Especially single target abilities are useless to run when you face 50+ enemy players at once. Most used are Proximity Detonation, Eye of Flame and Sap Essence. Worst about these abilities is that they all follow the caster. While most other abilities are ground based and are totally neglected by most PVP raids due to their underwhelming performance in most situations.
Yes, you read that right: healing bots. However these are not actual computer programs but players dedicated to healing and purging only. The game allows you to heal indefinately whilst being tanky at the same time. From own experience a healing bot is most often a Templar which is able to permablock whilst casting abilities. It also results into raids running permapurgers too. Rendering all damage over time into oblivion.
In the current version of the game (3.0.9) you are able to cast abilities whilst blocking. Which allows many classes and builds to be more tanky than ever intended. Especially healing bots benefit from blockcasting, since this allows them to reduce incoming damage whilst sustaining enough heals to survive massive damage.
Procsets have been semi-nerfed in the past by making them not able to critical damage. However many builds show that procsets are still overpowered in PVP. Dealing so much damage that most casual players won't even realise what hit them before turning into a pile of ash. For example the Worbels Revenge build by Fengrush shows how broken these sets are.