Royal bloodline costs more than illusion, AND is less likely to work. AND IT JUST STOPS YOU FROM LOSING THE FEW HP THAT ILLUSION LEAVES YOU LOSING.
It is seriously sucky.
I'd like to point out, in the Arena, the attackers have every disadvantage- Do less damage AND have limited resources,
Please limit the times they use skills in the Arena or boost attacker damage to be equal to that of the defender.