Server tick very much has an effect on this. It's not just HP/MP ticks. Server tick has to do with your placement on the map (As the server sees you, not how you see yourself on your screen). Ever notice how a Drk yoinks you in from what seems like twice the distance it should? Server tick. Guard goes off but you still get stunned? Server tick. You see 3 Recuperate heals go off but you die anyway through 1-2 people hitting you? Server tick. The server tick affects every single instance of feedback the game gives you from any button you press. It's awful, outdated, and needs to go but probably never will since the game is built so heavily around it.