Well, there's lag as in "hiccups" and "freezes" of the game, which are more or less pronounced and may be solved with the right fix.
And then there's lag as in "position check of characters 3 times per second" (~300 ms or so) that's built in the code of the game and considered "working as intended" by the development team, making it sometimes frustratingly impossible to dodge an AoE or evaluate one's distance to a running mob (resulting in this counter-intuitive "target is not in range" message when the mob's just next to you).
It is my contention that the former is a concerning issue (especially when it makes your team die 9/10 times on Titan HM -_-... talk about frustration), a circumstantial problem nevertheless; whereas the latter is a fundamentally flawed design. I really hope they make this position check twice if not even more often. Every time a skill is fired for instance, on top of 6 to 20 times per second, would be acceptable for an MMO that relies so much on movement and dynamic reactions to events, and claims to have a decent endgame. And if HL PvE is barely manageable as it stands, I don't even begin to see how PvP can work with such a lengthy server reaction time.
