The idea is that since he needs a crit from his passive in order to mark a target, he will need to either be very lucky, or he will have to spam skill 1 for more attack speed so he can land a crit. Since his int is low and it grows really slow, the hp to mana thing serves 2 purposes. First it gives you mana to spam skill 1 as needed, and second, it will be your main method for dealing damage to your mark. Although I kinda just got an idea I might throw on later.
And ya I know the concept isn't fitting the build, maybe this idea I have will help it along to fit my view.