The problem actually consists of 2 major parts.

First part is really connectivity. EU servers based in Canada are making EU players suffer from high network latency which can't be fixed by any means besides creating a dedicated EU datacenter. This is really expensive and requires both new hardware AND new office with new people. Would be a hard decision but I would go for it as SE cause because of it they are effectively losing EU subscribers.

The second and not the least part is the game design. The thing that really cosfuses people is the "animation lag", which is not the lag but a designed delay. I'll explain.

The boss has a cast (with a castbar) which is marked on the ground with a red area. At the end of the cast the attack should happen. What we are seeing is the red zone disappears and the boss actually starts his attack animation (which can be as long as 1.5 secs) and in the end of animation the attack happens dealing damage anf other bads like pushback in Titan's case. The thing is that the list of people effected by the attack is calculated right in the end of cast so people really have the animation delay to roam freely and get the attack when they are pretty far from the red zone.

The later should be definitely fixed by making the animation sync with cast bar and the effect be applied right when it should. So many skills are really effected by this "feature" that I can't even imagine PvP.

One more feature of FFXIV servers is that they do not really process data in a real time. They are doing internal cycles that process data which causes many consequences like ability delays and unpredictable DoT damage which do not tick fixed amount of times but do tick based on how many server cycles to actually fit in DoT's duration and it really differs from time to time.

While I like the FFXIV game very much I must admit that technically it is a disaster. I am patiently waiting for SE to even mention fixes for these misdesigns but do not currently see any. Probably I should get back to RIFT raiding and stop any efforts here.