Vigilances are a bit weird, because they are absolutely prey for any attack frigate - weak hull, weak shield, moderately slow, only 1 gun. Deploying them in early game where most frigates shine is rough.
But they pack a decent amount of missiles per DP (4.8 harpoons/DP without an officer), so are actually decent support ships (2% ECM by default and could be mounting another support mod in theory) in larger battles when there are enough forces around to keep them safe from attack frigates, and they have enough speed to avoid most destroyers and cruisers+. Treat them as tiny little Gryphons and assign them to escort a bigger ship. They can then also support that ship with an ion beam or with a heavy burst laser to help PD the flanks (and opportunistically fire off 8 harpoons at a time or more).
Honorable mention of course goes to putting a Salamander on them because of how FMR and Salamanders interacts. And ECCM makes Salamanders even nastier this version, though they lack the satisfying explosions that come from harpoon spam. They are by far the best salamander ship if thats your jam.