When it works, it's amazing, but it probably has the most trouble when you need it most. It's one of the reasons I like Lone Wolf on him. It's also the reason I like Predator on someone not Vessery. Predator is always active, no conditions to fulfill.
Predator on Vessery's spotter also let them just hang on to the Target Lock instead of needing to reacquire it for him each round. I'm not very mathey but my gut tells me that Predator+Focus on 3-4 dice is stronger than Target Lock on the same number of dice.
This is my experience, but that only really kicks in when you've got one big ship for Vessery to chew on for a while. That's great in the Fat Turret meta, but that's a less common than it used to be.
Or it lets you take a TL on the target you want Vessery chasing while still being able to take a modified shot on a different target.