I've got a grav/psy, but she's a little annoying to play. The cast time for psy is slow. The effect slooowwwwly reaches the target. I've had trouble against large groups in the past too. The damage and secondary effects are ok. Makes a pretty decent blapper, although with the pet and its repel, melee might not be as potent. Same with electrical - great melee in a poor melee environment. Personally, the best I've played (my personal play style) is grav/fire - mostly ranged attach and great globs of damage. Plays more like a blaster with a little control. Rather than a controller with more attack. You game play might generate different mileage 
I have a grav/psi. It can be potent if you focus on ST for most of your leveling but you have to watch your aggro. The biggest issue is that grav makes it hard to leverage Drain Psyche on a group and DP is something you want to use often. Wormhole can help with this but enemy placement is erratic. I slightly disagree with Singularity's repel being bad for blapping. The problem comes from fighting a group due to pulling other spawns. Fighting something 1 on 1 it gives decent protection/mitigation and draws some aggro away from the player.
I have no earthly idea where to start on slotting this beast. Going for ranged hell, would love to shoot for high recharge/permadom. Any help would be wonderful.
Thinking of trying a dom. Haven't tried one since villians first launched. I love gravity, always been a favorite. Would psy be a good fit, or maybe electric. Going to try and make a hovering Binary Singularity(i have the name reserved on liberty). Maybe widows for my ppp.