There are a lot of flaws in the PVP aspect of the game which should be one of the top priorities.
Melee Registration
People farm months for weapons like Demon Claws and end up having ghost hits like crazy, melee registration is the main source of damage for melee masteries and having ghost hits really effects spar outcomes a lot.
Projectile Update
The projectile update is one of the best updates however it messed up the hitboxes visually, U get hit by things that miss in your screen.
Auto-Aim
This feature is really noob-friendly for PVP, before it actually took skill to sub-punish and only a handful of players could do it.
Zoom-Mode
Recently we got zoom mode changed and it is really bad quality, Zoom mode used to be an option in old client and got many people using on it. Removing this option forced zoom-users to play on something they are not fimiliar with.
BI-Warrior
This speaks for itself.
Ofcourse there have been great updates for PVP and im not bashing anything, see this more of a list of things that need to be done.