I'm not sure how to address this. Human form is where all the team, utilities, and debuffs are. You can't leave it out and then complain you don't have them. You say that you have to constantly change forms, but isn't that the point of a shapeshifter class? Why pick shapeshifter forms if you don't want to, y'know, shapeshift? How much you do or do not shift forms is completely up to you. Want to blast away in Nova, go for it. Want to tank a bit, rock your Dwarf. Want to swap back and forth to keep things interesting, have at it. How you play is entirely up to you.
Nova attacks have a 1.2 damage modifier, the highest in the game, higher than Blasters. Dwarf has a 1.0 modifier, higher than Tanks and Brutes. The mez protection in Dwarf is FAR higher than what other melee sets get. You are correct there is no defense in either Nova or Dwarf form, and only a trivial amount in Combat Flight and Shadow Cloak. But you are forgetting that Cosmic Balance/Dark Sustenance boosts your damage, damage resistance, mez protection and can provide slow resistance, depending upon team composition. Electric Armor, Radiation, and Fiery Aura also lack any defense (Dark Armor gets a trivial amount in Cloak of Darkness) and most sets only get 1 or 2 debuff resistances while Regen has none.
The ability to change forms and fill multiple roles on a team is what they bring to the table. Need extra damage, go Nova. Need an off-tank, go Dwarf. Need extra control, healing, debuffing and other assorted utilities, go human.
I'm never against suggestions on how to improve an AT or set, but lets not misrepresent what it actually is and does before making suggestions on how to improve it.