I also got absolutely no help from this lot when I asked about expanding McMourning last week, so I wouldn't expect much response I'm afraid. Regardless, I will offer my experiences (a little limited in range I'm afraid).
Reva is in a tricky place at the moment because her card wants you to be deep up field to be able to use pyres and corpse markers as attack vectors, but she basically has no defensive tech. You can keep Shieldbearers nearby to absorb some incoming attacks, but you are basically paying 5 stones for defense that your master should probably have had on her card in the first place.
Happily Vincent is a bit of a house, he has decent offensive capabilities at both range and in melee. Shieldbearers can pack a punch and are good defensive pieces.
The first thing you will want for the Revenant crew is a box of Lampads, they are the best tool in the crew to utilise the pyre markers, pack a punch and are extremely difficult to actually kill.
McMourning himself is one of the best melee beaters we have in faction. He has a stat 7 melee attack that ignores pretty much everything, hands out injured and has a built in poison trigger with a moderate damage track. One thing that I have seen a lot of other people concerned with is giving McMourning himself added mobility. I have seen talk of Kentauroi and Dead Rider as options for this, as they both have the 'Ride With Me' ability. Otherwise, decent additions to the box seem to be Rafkin and Guild Autopsies.
I have mentioned the Dead Rider, but he is basically just a big fast beater. Gravediggers and Mortimer are decent if you need to generate extra markers for any reason, Asura Roten is just generically good everywhere (but I might hold off on a purchase for now, as she is good enough to be hit with the nerf bat imo) and the Carrion Emissary is good at board denial, adding zombies to the board and has a respectable combat output too.
My recommendation if you are looking to expand out from what you have already acquired is to buy into Molly and her Forgotten crew. She herself is a card drawing engine, her henchman is great at slowing down your opponents, Archie is (literally) a monster who has an easy leap and a massive damage track (at the expense of being able to concentrate - but hey, he is also immune to everything else too), The Forgotten Marshal is one of the best summoners in faction and the minions offer a whole range of skills from melee to very quick scheme runners with fly (seriously, Night Terrors are great). Molly is the one master I would be fairly comfortable running in any strategy (Reckoning is the weakest, but good news! you already own McMourning).
The three generic upgrades are generally very strong. The Whisper is useful for non-soulstone users who require certain suits/ results from their flips (Forgotten Marshal wants mid high crows for his summons for example), Grave Spirit's Touch is useful if you want to jam something right into your enemies crew (like Lampads) and Killer Instinct can turn your corpse/ zombie producers into a soulstone factory.