For single target i find it better to just cycle lift/crush/GD instead of casting 1 propel. The Inherent movement slows will stack and keep you out of melee. My dom is grav/nrg and with all the range attacks there is really no need for propel(despite it being the 2nd most fun power in the game. 1st being wormhole 
)
Wormhole is really just a copy of Flashfire or Stalagmites with a smaller radius and the teleport/knockback thrown in. Its as standard as the AoE hold in terms of its duration and recharge time and so on.
And I don't think Gravity has an edge in anything for Dominators.
For a Controller, it has good damage-per-endurance and single target damage, but these are very much diluted by Dominator secondaries.
The other plus point I guess is a tough defensive pet. Singularity will help you solo EBs safely, but its damage output isn't great, which is what you'd need for AVs.
All in all though, Gravity is a bit sub-par on Dominators. It gets the job done, but most other sets bring something extra to the table.
Wonderful write up of Dom stuff by Lileaceae in the Guides section. I love stuff like that. As pointed out there, Grav is not the best out of the box set for Doms. Still, it was my concept, and i am heading into the final leveling stretch and then purpling and running this beast.
1st question) As most know, Grav is light on area hold/control. However, with Permadom, isnt the aoe hold/creative use of Wormhole almost as good as having a number of AoE holds/controls in your powers but underutilized due to recharge? My logic is all Doms lean on their AoE hold, and they are all the same. At a certain point, you spam that and everything else is just fun times. (with the exception of fire/fire AoE gods of pain) But, my robot concept doesnt have flamethrowers, so on with the games. And truthfully, I just love the Grav special effects. Still trying to find an excuse to put throwing forklifts at enemies in my build. But again, with near 200% recharge, isnt the one AoE hold almost as good as having 4 AoE controls?
2nd Question) More of a follow up question. is there a Trade off. the i18 guide says Grav has good ST holds/damage. Now we all know that the big ST damage from Grav is not useful due to animation time (fun though). but still, when fighting AVs and such, does Grav do better because of it's ST stuff?