Short answer: If anyone's going to do it, it'll be a ranged combatant
Don't have the time to build such a monster, but I can make a few assumptions.
(This is assuming you're talking Orcus, the level 33 Solo Brute, although similar logic will apply to Orcus Empowered, who is a level higher but looks to have substantially the same abilities).
First: Orcus is rated as a difficult encounter for a full table of level 30s. To solo means that you're taking the full brunt of all his powers.
Second: You're going to want a striker of some sort (because you'll need to deal all 1525 points of damage), and that means you're going to be light on healing.
Third: Melee is right out. Touch of Death deals your bloodied value in damage on a miss, and auto-kills you on a hit. And it recharges. As a solo, you can't afford to be at half damage on your first round, with a 1/6 chance of eating the other half each round. And his at-will attack is Reach 4 as well.
Fourth: Orcus has a fly speed of 10. That means his effective range each turn is 24 (fly + fly-charge + reach 4). The good news is that he'll only get you for 3d12+12 damage. The bad news is that unless you get 15+ squares away on your turn, he'll be in range of Touch of Death next turn. (And this discussion assumes the GM throws you a bone and doesn't move-move-action point-Touch of Death. Orcus has two Action points, by the way).
So, put it all together, and the only character that's going to survive protracted combat is going to be someone who can shoot from very far away (I'm thinking Greatbow), and has a repeatable ability to move 20+ squares every turn. That turns the combat into one big aggro draw (as you get Orcus to chase you around while you ping him with arrows).
Alternatively, if you're allowed to choose the location of your fight, you just need to find somewhere that gives you a clear shot at him but prevents him from closing to within 4 squares. (He's Gargantuan, so any hallway would do.)