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Champions of Order and Orb of Imposition wizards effortlessly disable solo monsters. This one is no exception. This remains an issue with the paragon path and the class feature in question, not with the design of solo creatures. I reinforce my stance, the one which Wizards of the Coast shares and has been gradually adhering to judging from the evolution of its solo monsters in various sourcebooks, that solo monsters be created with extreme damage output and relatively low hit points in mind. This not only prevents the "slogfest" effect present in encounters with solo monsters, but also increases their threat level to be approximately equivalent to five standard monsters of an equal level. After all, five standard monsters shall be felled in roughly the same amount of time that it takes to overcome a 4x hit point solo monster, but the group of enemies is far more difficult to shut down with conditions and attack penalties, rendering them considerably more effective than most solo monsters in practice.
"Leader" is by no means a role for solo monsters. It is a designation for any monster whose auras or powers include one which directly provides bonuses, free attacks, hit points, temporary hit points, or other such benefits to its allies. Even if only one aura or power of the monster happens to match this criterion, it is designated as a leader nevertheless. Have a look at the Angel of Authority from page 8 of the Monster Manual 2, or the Couatl Star Serpent from page 38 of the same supplement. These two monsters each possess only one power that directly benefits their allies, namely, Majestic Rally and Couatl Radiance, and yet they are declared leaders nonetheless.