Yes, I was only proving a point that Blizzard attempted to create another Dark Templar hero which would be available through the campaign. But the lazy developers just used the Dark Templar hero that was available in vanilla StarCraft, in which couldn't be built by the Gateway, and renamed it to "Raszagal". After Zeratul destroyed the Statis Cell/Prison, then finishing Raszagal's dialogue reveals a regular Dark Templar portrait.
You could obviously tell the actual Raszagal unit has a Dark Templar wire frames and parenthesis, gives us a clue. The best thought that Raszagal was a Dark Templar unit to reveal Zeratul forced to murder Raszagal by Kerrigan in ending of the mission "The Reckoning". But instead they made her a Corsair with a Corsair's voice for no apparent reason that we know of.
Just in case I was questioned again about the rest:
As similar as to how Gerard DuGalle, Arcturus Mengsk and Aldaris. They tried to make Aldaris as a hero so you, the player, could kill him according to "The Insurgent" mission in the Protoss Campaign. Again, lazy developers replaced it with Tassadar renamed as Aldaris. From start to finish, you can clearly see Tassadar's portrait.
As for both Gerard DuGalle "Aleksander" and Arcturus Mengsk "Norad III", they're suppose to appear in both of the "Emperor's Fall" mission in which the ending reveals a meeting between DuGalle and Mengsk. Instead, they just used "Norad II" renamed to "Norad III" and DuGalle is just a standard battlecruiser. Before the conversation begins, you can clearly see Edmund Duke's potrait.
Then on "To Chain the Beast", at the end of the mission reveals a meeting between Duran and DuGalle as Duran introduces Kerrigan. The battlecruiser seen written as "Gerard DuGalle" with a rank underneath it "Admiral" is actually Norad II. Before the conversation begins or ends, you can see Edmund Duke's portrait again.
Though I answered the questions that weren't asked, I'm giving in my thoughts
why those uncompleted hero units that were truly meant to be seen in the Brood War Campaign. In which it makes sense why Aldaris is seen as a Templar, DuGalle and Mengsk as Battlecruisers, and Raszagal as a Dark Templar in the Editor. And in the Campaign that used Duke for both battlecruisers, Hero Dark Templar for Raszagal, and Tassadar for Aldaris are completely
permanent placeholders. Though the corsair is unintentional.
None.