Is it like that everywhere? I have been below 300 feet in Cozumel several times with trimix and I have also noticed a dearth of sea life. But then all my really deep dives there were in the north, near Playa San Juan and Las Rocas. Maybe at Maracaibo or Colombia it is more interesting at that depth?
You do have to go deep to hunt for lionfish. I don't see them much above 100 feet anymore. In fact, all my lionfish hunting dives there have been planned deco dives with some helium in the mixture. They're fairly bland, but they soak up whatever hot sauce or other savory flavors are put on them. They're also very low in fat (and therefore low in mercury and cadmium), so they're good to eat.