Tycondrius-- or rather... the current Tycondrius had lost the memories of his past self. For over two years, he had to stumble over pieces and fragments learned secondhand in order to assume his role enough for no one important to notice the difference.
Theoretically, Hades did not have that issue...
According to that gentle-orc... a notion reinforced by a certain Idiot, Tycon was previously known as Tyrael. The particular circumstances of how that was possible were unimportant.
That 'Tyrael' had enough power to challenge archangels and lizard gods at will.
Thus, it fell to reason... that 'Tyrael' would have friends and peers of similar ability, Hades being a prime example.
The Death Orc was an excellent resource. However, him having taken the godly domain of death and the dead, he was bound by the Laws, preventing him from interfering overmuch with the lives of mortals.