These delays has nothing to do with having 100 or even 200 ms, yeah it doesn't help but this isn't the main problem.
Try a game like WOW/Tera and play it with 100 ms and you will notice that it is a lot more responsive than ARR.

The main problem is SE making actions server side.
Which will feel like you have a delay, add some lag and you get this.
Yoshi stated that the server checks every 0.3 seconds where you are (which isn't true).

I would welcome a EU data centre but most of all I would welcome it if more stuff would be client side.
I'm pretty sure once that is there you won't notice the 100 ms all that much.

Side note the cast bar/animation and circles aren't programmed properly, it's called latency masking.

It's all these little things that make it feel sluggish, on the beta there was a big topic about it.
Back in SWTOR there was a topic about it.
It's called character responsiveness, often over looked but it's basically about how you experience the connection between you and the characters movement.

These delays make you feel disjointed but well.

What the game shows me isn't accurate so instead of that playing the game for me is learning what is actually going on and ignoring what the game tells me what is going on.
This does kill the fun though.