I'd say that maya is more suited to Maliwan. Some of her perks and class mods increase crit damage, elemental effect, and smg damage. Plus corrode, shock, and burn seems to go so much better with the siren theme.
Going by theme only Axton- Dahl, Vladof Sal- Vladof, possibly bandit Zer0- Jakobs Gaige- Torgue
Axton - TORGUE (anything explosive really) Gaige - Hyperion (Thinking line of shotguns specifically) Maya - Vladof (high RoF trumps better % for elemental damage every time) Salvador - Tediore (Quick reloads are a must as he is all about keeping up a steady stream of bullets) Zero - Jakobs (If it took more than one shot you weren't using a Jakobs)
Axton: Torque, really no substitute dps wise Gaige: Maliwan for Rubi, otherwise Hyperion for gun dps Maya: Hyperion + Cat gives highest gun dps Salvador: Torgue + slag, or certain Torgue/Torgue for god mode Zero: Vladof- Rapier, White Death, Infinity, Kitten covers everything good but Rubi.