When tanking mutiiple enemies should I switch targets a lot? In other games mainly FF14 I had to switch targets a lot in order to gain threat on all enemies in a group, but in this game it doesn't seem to work the same way

The tldr of threat is that as combat starts, you will have double the threat of other players in the group, however, all abilities players will increase their threat to each target, what tanks normally do is that they identify the more difficult/damaging enemies and maintain aggro of those. Assume for example that you have a pack of adds or a boss fight in which there are 5 targets, there is no way that you would be able to maintain aggro of all, so you identify which would hurt the most (are they bosses, gold/silver/trash tier etc.) and keep aggro of them.

 

Assuming you do open world/flashpoints/uprising or other storymode level content it doesn't REALLY matter that much if you screw up and something ends up hitting a healer or a DPS, just make use of your AoE abilities to maintain aggro of multiple enemies. Using line of sight, pulls, pushes, stuns and other things helps a lot with maintaining aggro of multiple enemies who were initially spread out as you can damage all of them at the same time and thus build threat of each of them.