I've always experienced that delay regardless of ping, and I've played on multiple connections with powerful home-built computers that easily play the settings we have.
There is a very small amount of time in which abilities and their ground/cast markers don't match up. So sometimes a person thinks they just made it and...nope.

I've done plenty of MMO hopping to have never encountered this anywhere else. at all. ever. They may have had random spikes, but not a constant delay that is noticeable in every incoming and outgoing casts (I see it in the heal cast too, I can start moving about 0.5 seconds before my cast ends and not interrupt myself)

I've adapted to it because it's not a huge delay, but then again I play a ranged character.
My husband plays a tank and a few times he thought he got out of a major swing attack in time only to be hit. It frustrates him a bit, but I'm sure he'll adapt over time.

It wouldn't kill them to at least look into it. Whether they actually do anything about it or blame the player, well, that's up to them. But to imply that a NA person on an NA datacenter with 100/75 Mbps needs an internet upgrade for this one particular game and no other game at all just seems silly.