I've mastered my targeting for my personal needs as a tank and I stick to the target filters and managing my LoS, but Akuha's tip was a good one for what you're asking. If you're using the L2 crossbar skills then tap R1 to target nearest, and alternately if you're using your R2 crossbar skills use your L1 to target nearest.

@Bixby, X should do that but fails too often for whatever reason and then you're switching to your DPAD to scroll across to the one you want. For whatever reason the L2/R1 R2/L1 functions better, and if it misses the target you can easily flip through targets in your LoS.