The ring that displays under your current target needs to be revised at some point. The one they have right now seems to be a static texture of the sorts that is just stretched out based on the target radius, then it's tinted by whatever colour you have for the name of that kind of target. This is problematic in a lot of ways, particularly on larger entities. The ring is just a big ugly mess when it grows in size that somehow actually sucks at conveying information.

Any game development tool would allow you to instead have the circle itself drawn dynamically for the size that it's needed, ensuring that it is crisp and clear. Furthermore, graphically the ring under your target should either graphically be drawn on a UI level, or drawn later in the graphics processing cycle. In plain speech, this would have it visible even when there are explosions and stuff. For the less technical-savvy, you see similar things in games where an outline can be drawn around targets through a wall.

One element in particular that requires special attention is the little arrow that shows where the target is facing. FFXIV has encounters like O11 or the first and last bosses of The Copied Factory where the boss has a really symmetrical shape and it can be more difficult than it needs to be to read which way it is facing at a quick glance. In a case like O11 for example, in a screenshot when it is still it's easy to tell, but in combat with explosions and stuff it can be hard to tell its butt from its face, which generally has people just know which way it is facing by memory or precedent rather than visual identification.

While I do have my effects visible for party members on, a great many players have them set to Limited due to readability issues, and I think a few simple techniques could alleviate that.