Grav/FF is my current main and he solos quite a lot. Nothing much bothers him, not even Romans (on 4th diff).
My slotting is probably different than most.
I slot crush for damage, and GD 2acc, 2dam, 1hold, 1rech which is perfect solo and more than good enough on teams.
Wormhole is 2acc, 2rech, 2range as I find it's range a little too limited for my tastes. The 2rech makes it ready for almost every fight (solo).
If I want to grab just a single target then I do it with tp foe.
My normal tactic is to wormhole (from cover) into a wall, mass immob everyone, place holds on the most annoying targets, and use propel and crush to squeeze the life out of them one by one. If there is someone causing me serious trouble then detention field handles him until I'm done with his buddies.
Most targets go down surprisingly quickly.
In a group I find that my bubbles are really my primary purpose. Wormhole is hard to use on a fast moving team, and detention field is, well, VERY situational.. I simply hold the most dangerous targets, immob the remainder, and let the rest of the team do what they do best...
Oh, and repulsion bomb does NOT benefit from containment *grumbles* though it is a nice backup control power.
NS