I really enjoy playing controllers, solo and in groups and I was very excited to see this brought up. I will however spare everyone from the essay on controller soloing I wrote during lunch and focus on adding some additional tips.
Regarding containment, it applies to primary, secondary, power pool, and ancillary/patron powers but not temporary or prestige powers. I don't think it even works on brawl. But since it includes power pool attacks it's worth considering them for a soloing controller. I was looking at the numbers on them but I had Mids open and it's not current. In the past though Air Superiority was a good filler attack for controllers. It does about the same damage as most controllers' single target hold, has good endurance cost, casting time, recharge, and animation, and has a nice -fly effect which may come in handy. If you were running Illusion Control I would look at the fighting pool's boxing because it's got a decent chance of a weak stun, though it's lower damage. I'm actually going to test out the pool attacks and see how they're working.
When picking powers as a soloer just remember any power that buffs a teammate only is dead weight until you have a pet, so probably pass on those powers until you have a pet, or respec at that time. Of course this also means a buff-heavy or heal-heavy powerset may not be your best choice though again once you have your pet then you can make them even stronger.
I'd also like to point out that this game does support dual builds, though you have to slot them separately and until we're all running around with 50s to bankroll our lower level characters that may be tricky. But it's an option.
Finally if you're trying to figure out which controller power set has the most native single target damage, hands down it's Gravity Control. With Lift and Propel it has 2 direct attacks that far outclass any single target attacks other controllers get. Though Fire has some nice aoe damage, it really only blows up big if you're playing a Kin, but then it really blows up.