Blight scales up faster than Bleed. At like Rank 4 skill, Blight is 5 damage a turn up to 15 per turn, Bleed is 3 a turn up to 12. Bleed reduces in damage faster. Blight continues to do higher damage for longer. Granted, bleed attacks actually deal damage when the attack that applies them hits, but, short of crits that damage quickly seemed swallowed up by Blight's higher overall damage.
Plus tons of shit likes to resist bleed at average to good levels. Other than the Warrens, most stuff seems more vulnerable to Bleed. So whereas you might have to buff up the Jester's bleed with a trinket to get consistent application, Blight doesn't really need it.
The Jester isn't terrible. I think it's a "fun" class. I just think that in terms of damage, virtually everyone does it better and faster. Stress healing is the only real thing he has going for him above everyone else. Basically, use Jester if you like playing risky or doing risky things like having Clown Shoes try to Dodge tank, or if you like that 4th rank buffer. (I don't use them, frankly. More damage per turn > buffs.) Otherwise, I think almost every other damage class gives better results. I sort of feel similar about the HM, but, he can attack any rank from almost any position, self-heals, has an active defense ability and a great debuff. (Forget Marking for damage. Marking for reduce Prot is arguably just as good if not better.) He's way more flexible than the Jester without having to change ranks or debuff himself for the privilege.
That said, I ALWAYS forget to give the dog their treat during boss fights. Always.