I already avoid exceeding dissipation when I can. Does not always save a frigate when it gets focused by a capital or multiple ships. Gets annoying when a frigate is in the path of at least half the enemy fleet beelining toward the point it just captured when the rest of my fleet is scattered and may not arrive in time to help.
Currently, I use fewer big ships plus about three to four frigates for point capping and minor harassment. My fleet composition varies depending on which ships need to be fixed by Hull Restoration. While my fleet is almost endgame ready, it is not strong enough (yet) to handle the toughest fights without too many casualties.
Vanguard is convenient as an enemy drop (when I use Field Repairs and Hull Restoration), and does what I need it to do, which is cap points and distract, and I do not care much if it dies. I do not build or buy them, no need to.
I am at the point when I have money to burn (but not too much to afford restoring everything), but not time to wait for Hull Restoration to fix all the d-mods (and not rich enough to restore ships aside from frigates under 50k), so I am still averse to casualties with ships I care about. Vanguard is one of those, "Ah! clean hull dropped from the enemy, I'll use it!" If it dies, no problem. If it lives and stays pristine, I will add it to my reserve ship collection. Occasionally, other ships with only one or two d-mods drop, and I use them too if I have the weapons on hand. Vanguard just happens to drop with less d-mods more often thanks to Rugged Construction, and it is less junky than Cerberus or Hound.
Currently, my frigates are three Tempests, one Scarab, and one Omen. Vanguards I use are usually looted from the enemy, armed up, and sent to fight more bounties instead of my more permanent fleet members until I return home.