Heroes: Tank - large naga able to take hits. Should have some way of distracting enemy units, like Taunts or having an aura that weakens their attack power.
Disruptor - quick, agile unit able to get in and out quickly. Should have poison abilities, and maybe some nets to stop enemy movement. May not have to cloak.
Spellcaster - Able to wield many different spells focusing on water or ice. may summon water elementals or revenants (to be slightly different from other spellcasters). Could have Blizzard, Frost Shield, and Frost Nova. Spells open for replacment depending on other water spells.
Sea Witch - ranged hero with Forked Lightning, Mana Shield, Frost Arrow, and Tornado.
Attacker - Naga Deathknight previously serving the Lich King. Melee attacker and has many abilities, like summon Ghouls (timed), Death Coil, Vampiric/Command Aura, and Death and Decay.