Wow, so many replies. Thanks for all the different opinions. I want the discussion to be visible.

For those who shot down my ideas (weather/day/night-only mobs, mobs that aggro to different senses than sight, and mobs that are weaker or stronger than average) what kind of suggestions could you propose to increase the Risk/Reward dynamic for FFXIV 3.2 and beyond? Maybe I'm not on the right track with the solution, but I think I'm definitely on track with the problem description.

The recap of my suggestion is that some mobs aggro to different senses. Sound, low HP, use of magic in proximity, etc. And some mobs be stronger than average, some weaker. For example, a lv55 mob normally has such and such HP and such and such ATK/DEF stats. Randomly, when mobs in that area spawn, some could spawn with 10% higher or 10% lower stats. (Okay, maybe 10%ATK/DEF is not the right bracket, but this is the idea). They'd look the same and have the same skills, but they might be stronger than you expect, or they might be weaker. This makes running up and hitting it in the face more engaging, because you might be in for a surprise. In my own ideal case, I'd like the "stronger" ones to be able to kill you if you aren't careful. Or maybe 1 in 100 of them will just be strong enough to be able to kill you unless you run away or out-level it.

Does this break the "EZ FACEROLL" of open world encounters? Yes, yes it does. And I think that's a good thing. But maybe you've got other suggestions to add risk and reward back into FFXIV.