Casters have 17% base chance to miss vs raid bosses.
Melee have 8% base chance to miss, and a 27% chance when dual-wielding. Special attacks (all yellow damage) do NOT suffer from a dual-wield penalty.
Melee ALSO have 6.5% chance to be dodged on top of misses, which can be mitigated by expertise.
Melee ALSO ALSO have a 15% chance to be parried on top of dodges and misses, which can also be mitigated by expertise, but melee dps should be attacking from behind so this shouldn't matter for non-tanks.

Thus the only stats that increases your chance to hit are hit rating and expertise rating (for melee).