Legendary Holster is an awesome card! It was underrated until A-2-3 decks came up. These decks have around 80% chance to succeed the holster pull since there are still rogue values (jobs and the holster itself). You may want to include 4-values like the costly Ambush if you can equip 3-bullet dudes (Ramiro Mendoza...)
Fighting with or against this type of decks is all about winning lowball because you want to ace someone first. I mean before your opponent can reduce your bullets, send you home, play Unprepared or even kill you with another Holster ;)
Attached to Angélica Espinoza it can be very frightening even though her ability makes you losing initiative. You will also want to abuse of grifter abilities to get the holster early. Travis Moone or The Fixer are good candidates.
I think this card is meta-defining since it forces to include cards and adopt strategies to counter it.