They're timed, but not so much IRL as it is in-game time (ET Eorzean Time). Most unspoiled nodes spawn at each AM/PM of their time. For example, the unspoiled node for Adamantite Ores will spawn at 11a.m. AND 11p.m. ET. This means every 30min IRL, the node will spawn. I really wouldn't consider this poor design, given that they want to it have some moderate degree of rarity (similar to how its been since 2.0 launched), and not just something you can freely bot for 24hrs a day non-stop.
Thank you so much for clarifying that information. When I read about certain nodes being up at like 11 am/11 pm for example I figured it meant REAL time. Every 30 minutes is much much more manageable. This I can live with. Thanks.