I just went to carno island with a high level argy and started wiping out the raptors, sabers, carnos, and scorpions. Within 10 minutes 2 rexes spawned, one being a tek rex. After clearing out for another 3 ish minutes, 2 more rexes spawned, one being a level 145. Seems like an effective way to find high level rexes Becuase I can’t find them at their other spawn locations around the island.