Go mind and slot for damage with levitate, domination and mesmerize. More damage and 31 levels earlier too ;-)
In all seriousness if you are so keen on a pet, I think Phantasm is the second best choice however Illusion Controls lack of containment means you will lose some damage from your epic blasts.
I can't speak for Animate Stone or Phantasm, but of the sets I have played I would say Fly Trap > Jack Frost > Singularity. Jack hits harder but spends a lot of time running around between targets and generally getting killed. Since they fixed Fly Trap I find that it puts out a decent amount of damage. It has the added bonus of 2 AoE attacks. While Singularity is less damaging, it makes up for it in control and survivability. Its like having another gravity controller on the team (with tank resists).
I forgot to mention that my secondary will be empathy so I could buff my pet. I still want to do control with my primary, but I want the extra damage from the pet after its buffed.
lvl 50 - Elec/WP/Mu Mastery Stalker, lvl 50 - Dark/EA/Soul Mastery Stalker, lvl 50 - EM/Nin/Soul Mastery Stalker
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Stone might be a good choice then, it has some of the best control in the game and 'animate stone' is a great pet to be buffing. Some of the Earth EPP's also are pretty good and then would fit thematically.
Some kind of earth druid or spiritual healer (native american flavours)
Alternatively Plant is also an option. Singularity is more about control then damage, so I would remove that from your shortlist. Also gravity as a whole is pretty weak at control and you'd likely become a slave to your secondary.
I have all the pets except Singy, and I'm getting close there. I would say that Phantasm is the second highest damage. He is an energy blaster with a single target blast and Torrent, a cone. He also uses his decoy, which does Illusory damage that does not heal back if you defeat the target fast enough.
Animate Stone a/k/a Rocky is now the next highest, since he uses Seismic Smash and he is not subject to mez.
It is hard to say between Fly Trap a/k/a Audrey II or "Twoey" and Jack Frost which is the highest damage. Both are decent.
LOCAL MAN! The most famous hero of all. There are more newspaper stories about me than anyone else. "Local Man wins Medal of Honor." "Local Man opens Animal Shelter." "Local Man Charged with..." (Um, forget about that one.)
Guide Links: Earth/Rad Guide, Illusion/Rad Guide, Electric Control
I think "Rocky" is a real good pet. It's debatable which pet has the most damage, but "Rocky" is by far the toughest. Sure, Phantasm is really surviveable due to his decoy he summons, but he's more tricky, not tough. 
Rocky has strong resistances to everything (add in a resistance IO unique and it's even better), has mez protection, and is immune to psi damage. Give him some buffs, and he's really strong, and can easily tank for you. He cycles seismic smash, stone fists, and hurl boulder. He's quite nice. Just a bit ugly!
I wouldn't say the stone pet is "by far" the toughest. The singularity is just as tough as it is (50% resist to all damage types, immune to psionic/toxic), plus it has repel to keep things away from it in melee.
Singy's only real downside is that it doesn't hit as hard. But it cycles its attacks pretty well, and I've watched it solo a +1 boss without any assistance from me.
The Mastermind Project
Leveling every primary/secondary to 50!
50: Bot/FF, Bot/Dark, Ninja/Trap, Merc/Pain, Necro/Dark, Thug/Dark
Works in Progress: Thug/TA, Merc/Poison, Thug/Pain, Ninja/Pain, Thug/Storm
Singy can't be healed. That puts it at a distinct disadvantage over Stoney (Depending on your secondary).
What about the Jack Frost?
lvl 50 - Elec/WP/Mu Mastery Stalker, lvl 50 - Dark/EA/Soul Mastery Stalker, lvl 50 - EM/Nin/Soul Mastery Stalker
New Toons
lvl 21 - StJ/WP Stalker
I don't have an Ice controller that high, but I hear that Jack gets stuck spamming his Sword attacks while ignoring his snowball and freezing touch.
The Ice pet does fine damage but dies in half the time of the Earth pet.
Basically having a pet is like having a sidekick. I'd compare the Ice and Plant pets to level 15-ish Dominator sidekicks with perma-Thermal shields on them. Fire would be like a bunch of low level (pre-armor and mezz protection) Scrappers. The Earth pet is like a level 30-ish tanker who has around 6 attacks and no Taunt.
In my experience with my Ice Dom, Jack cycles through his attacks reasonably well, although he tends to use Ice Bolt once before rushing into melee and chaining his melee abilities. This isn't such a bad thing though, since I recall that he has a debuff aura (slow and -recharge, like most ice abilities), and his melee attacks seem to hit harder from what I can tell.
Other than the Imps, which you mention that you did not want, the only other Controller pet I've used is Phantasm, who's quite awesome. I don't really mind the knockback, and it was basically a non-issue grouping since I solo'd the entire way with my Ill/, but if you plan to team a lot it's something to consider.
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Singy can't be healed. That puts it at a distinct disadvantage over Stoney (Depending on your secondary).
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Yeah, Singy can't be healed or buffed, which is why he's as tough as he is. The earth/thermal I'm tinkering with might be pretty fun, once I get all my powers together. Put both shields and forge on the rock, and let him go to town. 
The Mastermind Project
Leveling every primary/secondary to 50!
50: Bot/FF, Bot/Dark, Ninja/Trap, Merc/Pain, Necro/Dark, Thug/Dark
Works in Progress: Thug/TA, Merc/Poison, Thug/Pain, Ninja/Pain, Thug/Storm
Just to clarify, Singy can be buffed. Just not healed.
Also: Stoney+Fulcrum Shift=Good Times.
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What about the Jack Frost?
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Jack is a fine pet. He generally throws a snowball from range, then runs into melee. He cycles his Freezing Touch pretty well . . . he also has Chilling Embrace, slowing the foes. He does die a lot faster than Rocky.
LOCAL MAN! The most famous hero of all. There are more newspaper stories about me than anyone else. "Local Man wins Medal of Honor." "Local Man opens Animal Shelter." "Local Man Charged with..." (Um, forget about that one.)
Guide Links: Earth/Rad Guide, Illusion/Rad Guide, Electric Control
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What about the Jack Frost?
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Jack is a fine pet. He generally throws a snowball from range, then runs into melee. He cycles his Freezing Touch pretty well . . . he also has Chilling Embrace, slowing the foes. He does die a lot faster than Rocky.
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He cycles attacks better than he once did. He is a good, solid pet, and much more useful than Back in the Day, and I really like him. But he was the first pet I ever got, and my observation then still holds true:
"Jack Frost: Heart of a Lion, brain of a Duck." 
"How do you know you are on the side of good?" a Paragon citizen asked him. "How can we even know what is 'good'?"
"The Most High has spoken, even with His own blood," Melancton replied. "Surely we know."
Both Jack and Stoney do great damage, but Jack has problems surviving it. Phantasm does ok damage, Singy and Flytrap do mediocre damage.
If you want the pet for damage, then go Earth control. You have to realize that earth does almost no other damage though so don't look for an Earth/Emp to be able to solo well till after 44. If you want to be able to solo an Empath, then Illusion/Emp is very strong.
My ice troller with thermal secondary is pretty nice. Buff jack with shields and forge and then debuff mob. they don't stay up for long.
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I forgot to mention that my secondary will be empathy so I could buff my pet. I still want to do control with my primary, but I want the extra damage from the pet after its buffed.
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Radiation is probably a better set for this purpose. It also synergizes better with the control. It also combines buffs and debuffs, which is far more effective than Fortitude.
If it's more for the healing aspect, Thermal Radiation is a good comprimise as well, in that you have the equivalent buff to Fortitude, but you also have more utility in Heat Exaustion, Melt Armor, and your resistance buffs.
Don't get me wrong, done right Empathy is nice, but groups don't go 'GAWD WE NEED AN EMPATHY GUY FOR THIS' as much as they go 'GAWD WE NEED RADIATION'
I currenlty have a Pain corruptor with the epic pet and he does pretty good and I was wondering what pet for the trollers does the most damage? I already have a Fire controller and I do not want to repeat that set. So my set selections are the following:
Ice Control
-Jack Frost
Gravity Control
-Sing
Plant Control
-Fly Trap
Earth Control
-Animate Stone
Illusion Control
-Phantasm
lvl 50 - Elec/WP/Mu Mastery Stalker, lvl 50 - Dark/EA/Soul Mastery Stalker, lvl 50 - EM/Nin/Soul Mastery Stalker
New Toons
lvl 21 - StJ/WP Stalker