the holy trinity idea didn't survive the 1.11 nerfs to Malice. it doesn't work anymore.
the battle-ball strat still requires mulitple cap ships though, but there's no longer a specific interaction you're trying to exploit, just general synergy.
mothership shield regens the guardians (and turns on Malice if you've got enough antimatter).
radiance AM burns enemy cap ships and generally just protects your own caps from enemy caps by blowing them up with Cleansing Brilliance.
halcyon screens your battleball from strikers with TK Push and also provides passive damage boost.
rapture is a very important defense against large fleets of LRMS or Lights or Heavies. Vertigo really screws up the damage on any direct firing ships. passive squadron damage boost is just gravy (but still very good).
every advent fleet will eventually want at least 1 of each of those 4 cap ships. the order you build them in might vary a lot depending on game circumstances though.