The AoE Immobs are a bit dangerous, they are most useful for keeping a group in one place if you have another mez on them - in your case in would be Flashfire - Fire Cages will stop them wondering about and the Flashfire will stun them, you can then use an AoE attack from Assault on the group.
In general, what you say in the first paragraph works well until you are higher level and have the AoE mez powers and attacks slotted with SOs, before that the AoEs tend to get you killed.
I found tp foe an Incredibly useful power for my early levels as a dom. (Ice/Fire)
tp foe - hold - beat into a pulp - repeat.
i had 2 accs in it (for pvp purposes later on) the only big problem is the occasional aggro draw. Well that and it makes it sloow going, but it is pretty safe.
Hmmm with my fire I didn't take firecages cause of the agro, have remade my fire and wont be taking it this time. I found I was a damn fine single target killer, but until I had more agro control I had no intention of taking on the world in one go.
"Well, they found my diary today.
They were appropriately appalled
at the discovery of the eight victims
They're now putting it all together.
Women wrapped in silk
with one leg missing
Eight legs, one body, silk,
spider, brilliant!"
I've not played a Dom up to high levels yet, but from lower-level experience of two different Doms and a ton of Controllers, I can't say I generally bother with the AoE immobs. Especially for Doms, where they last less time when you're not in Domination. They use up quite a bit of endurance, bring in a load of aggro, and don't actually incapacitate the enemies. The best uses I've seen are either stacking them with AoE disorients, or immobing a group while the team escapes if you all need to run. I generally find my single-target controls and keeping moving is enough to make sure I don't take too many big melee hits.
One Vs one or against small groups (3-4 inividuals) I have no probs, I can throw out my mind/psi stuff and melt their feeble brains.
It all goes wrong if I use the mass sleep power, they all fall asleep someone near by breathes, they all wake up and come looking for me :O
But hes only lvl 8 so plenty of time to learn new wonderous ways to kill things 
Loving the whole Dom experience. I am playing Violet Jameson, a lvl 24 plant/thorn dom and my usual tactics are as follows:
rush in and chuck Seeds of Confusion (3 x Confuse slotted) with optimal AoE.
when enemies cluster and start bashing each other, then chuck Rooted, thorn burst etc etc to keep them in place and to cause enough damage that the xp isnt wasted.
If any stragglers, then impale, strangle vines, etc keep them in place till the fighters can finish them off.
Superb in a large team with bigger groups.
Ahh, tactics
Im gonna tell u what i always did when i played my dominator grav/psi lvl38...
Target enemy. Stay behind a wall. Wormhole all of the pack to a wall.
With this tactic, u will have them packed, knockedbacked and disoriented all of them in a wall, undeffensed all of them... Then i just spam the attacks/controlls powers as demand the situation.
Add this the other situables powers if things go wrong (DS,GDF,...) and a mini-dominator pet (singularity) and u will have a cakewalk at any dificulty lvl.
PS: WORMHOLE = Tricky power... TP FOE + KNOCKBACK + DISORIENT in only 1 power...
PSS: the shame is u need to go until lvl26 without it, and unslotted, isnt so nicer than it could be.
BTW, im neither with the inmobs, as other ppl said b4... and, man, AoE inmob = aggro magnet = nice faceplant. Just skip them
Dominator tactics...
In a team: use an AoE immob and die.
No but seriously, the tactic is to (in a typical 1 Lt 2 minions situation) to hold the Lt and bash off the minions, then go for the Lt.
If you're a Plant/, use Seeds of Confusion and proceed to control the ones it missed. When there's only a few left, hurt each of the mob, cones help a lot on this and they will annihilate eachother pretty soon. (Longbow Flamethrowers ftw)
Corruptor rain powers do fantastic total damage but have the unfortunate effect of making mobs flee the area. Flashfire + fire cages + corruptors firing off AoEs = dead mobs fast.
Also you can AoE immob a group of mobs around a corner or from behind an object by just having line of sight to one mob on the edge of the pack. That way you don't get hit and you can prevent large spawns from swarming your team.
There are plenty of uses but like people say, if nobody has aggro and you hit AoE immob in plain sight of mobs then you will have all the aggro. You just have to be sensible in using it.
The main reason to take fire cages is the fast recharging combination of flashfire and fire cages effectively being a ranged AoE hold.
well as a last resort, i have taken up stealth at low levels and then superspeed later just incase I end up near death, hady for an escape plan
Hi
Been trying out a dominator. Loved the first few levels.
Had 1 single target hold, a range and a close attack.
Was moving around, a hold here, back off to here, blast a guy, run in and finish with the melee attack, run away, hold there, move, burn, burn, move.
But now I have got fire cages - AoE immobolise things have changed. It's usefull but I'm not sure if I wouldnt be better off sticking to single target stuff.
The AoE Immo with domination going probably get through the end of a duo'd mission last night. Not sure how we would have done with just STs but then I might be back to doing more moving about, kiting backwards, holding here and there whilst blasting to seperate a group rather than having the whole lot aggro'd.
any thoughts ?