Bah-- my tyrant is this:
Defiler Tyrant
–Old Adversary, Hive Commander, Shredder Beetles, Psychic Scream, Leech Essence, Devourers, Lash/Bone Sword.
3 Guard with Lash
The unit is expensive, however, the Tyrant fires 3 guns a turn and is a Beast in combat. As well as aiding the rest of the army.
However, if you are gunna go with the configuration that you are looking at you should do this:
Tyrant
–Old Adversary, Leech Essence, Devourers, Lash/Bone Sword, Paroxysm.
Still two guns a turn, and much much better close combat for the tyrant and for the army.