Having gotten a Earth/TA back in the hold days, I can confirm that you lock stuff down. Killing stuff on the other hand is a different story, although your pet does do some nice dps this build is more for group play then anything else.
Volcanic Gases is one of the best AOE holds in the game due to it's pulsing nature. Slot it with a Lockdown: chance for +2 Mag Hold you get multiple chance to proc it (where as other AOE holds, you only get one shot at activation).
I was able to dig out one of my old builds if you want at least a idea of a build.
Hero Plan by Mids' Hero Designer 1.962
http://www.cohplanner.com/
Click this DataLink to open the build!
Level 50 Magic Controller
Primary Power Set: Earth Control
Secondary Power Set: Trick Arrow
Power Pool: Speed
Power Pool: Leaping
Power Pool: Leadership
Ancillary Pool: Fire Mastery
Hero Profile:
Level 1: Fossilize
(A) Basilisk's Gaze - Recharge/Hold
(3) Basilisk's Gaze - Accuracy/Hold
(3) Basilisk's Gaze - Accuracy/Recharge
(5) Basilisk's Gaze - Endurance/Recharge/Hold
(5) Basilisk's Gaze - Accuracy/Endurance/Recharge/Hold
Level 1: Entangling Arrow
(A) Trap of the Hunter - Accuracy/Recharge
(48) Trap of the Hunter - Endurance/Immobilize
(48) Trap of the Hunter - Accuracy/Endurance
(48) Trap of the Hunter - Accuracy/Immobilize/Recharge
Level 2: Stone Cages
(A) Debilitative Action - Disorient Bonus
(7) Trap of the Hunter - Chance of Damage(Lethal)
(7) Trap of the Hunter - Accuracy/Endurance
(9) Trap of the Hunter - Endurance/Immobilize
(9) Trap of the Hunter - Accuracy/Recharge
(42) Trap of the Hunter - Accuracy/Immobilize/Recharge
Level 4: Glue Arrow
(A) Slow IO Level 6: Quicksand
(A) Slow IO Level 8: Hasten
(A) Recharge Reduction IO
(31) Recharge Reduction IO
Level 10: Ice Arrow
(A) Basilisk's Gaze - Accuracy/Hold
(11) Basilisk's Gaze - Accuracy/Recharge
(11) Basilisk's Gaze - Accuracy/Endurance/Recharge/Hold
(17) Basilisk's Gaze - Endurance/Recharge/Hold
(17) Basilisk's Gaze - Recharge/Hold
Level 12: Stalagmites
(A) Stupefy - Accuracy/Recharge
(13) Stupefy - Accuracy/Stun/Recharge
(13) Stupefy - Accuracy/Endurance
(15) Stupefy - Endurance/Stun
(15) Stupefy - Stun/Range
Level 14: Super Jump
(A) Unbounded Leap - +Stealth Level 16: Poison Gas Arrow
(A) Call of the Sandman - Accuracy/Sleep/Recharge
(46) Call of the Sandman - Accuracy/Endurance
Level 18: Earthquake
(A) Achilles' Heel - Chance for Res Debuff
(19) Dark Watcher's Despair - To Hit Debuff
(19) Dark Watcher's Despair - To Hit Debuff/Recharge
(25) Dark Watcher's Despair - To Hit Debuff/Recharge/Endurance
(40) Dark Watcher's Despair - To Hit Debuff/Endurance
(40) Dark Watcher's Despair - Recharge/Endurance
Level 20: Acid Arrow
(A) Achilles' Heel - Chance for Res Debuff
(21) Analyze Weakness - Accuracy/Defense Debuff
(21) Analyze Weakness - Accuracy/Endurance/Recharge
(23) Analyze Weakness - Defense Debuff/Endurance/Recharge
(23) Analyze Weakness - Defense Debuff
Level 22: Combat Jumping
(A) Karma - Knockback Protection Level 24: Assault
(A) Endurance Reduction IO
(25) Endurance Reduction IO
Level 26: Volcanic Gasses
(A) Lockdown - Chance for +2 Mag Hold
(27) Lockdown - Accuracy/Endurance/Recharge/Hold
(27) Basilisk's Gaze - Accuracy/Endurance/Recharge/Hold
(29) Basilisk's Gaze - Endurance/Recharge/Hold
(29) Basilisk's Gaze - Recharge/Hold
(34) Basilisk's Gaze - Accuracy/Recharge
Level 28: Disruption Arrow
(A) Endurance Reduction IO
(37) Recharge Reduction IO
(40) Recharge Reduction IO
Level 30: Tactics
(A) Endurance Reduction IO
(31) To Hit Buff IO
(31) To Hit Buff IO
Level 32: Animate Stone
(A) Expedient Reinforcement - Resist Bonus Aura for Pets
(33) Expedient Reinforcement - Accuracy/Damage
(33) Expedient Reinforcement - Accuracy/Damage/Recharge
(33) Sovereign Right - Resistance Bonus
(34) Expedient Reinforcement - Endurance/Damage/Recharge
(34) Sovereign Right - Accuracy/Damage/Endurance
Level 35: Oil Slick Arrow
(A) Achilles' Heel - Chance for Res Debuff
(36) Touch of Lady Grey - Chance for Negative Damage
(36) Impeded Swiftness - Chance of Damage(Smashing)
(36) Positron's Blast - Damage/Recharge
(37) Positron's Blast - Damage/Endurance
(37) Positron's Blast - Chance of Damage(Energy)
Level 38: Fire Ball
(A) Positron's Blast - Damage/Recharge
(39) Positron's Blast - Damage/Endurance
(39) Positron's Blast - Chance of Damage(Energy)
(39) Positron's Blast - Accuracy/Damage/Endurance
(42) Positron's Blast - Accuracy/Damage
Level 41: EMP Arrow
(A) Lockdown - Chance for +2 Mag Hold
(42) Lockdown - Accuracy/Endurance/Recharge/Hold
(43) Energy Manipulator - Chance to Stun
(43) Basilisk's Gaze - Accuracy/Endurance/Recharge/Hold
(43) Basilisk's Gaze - Endurance/Recharge/Hold
(46) Basilisk's Gaze - Accuracy/Recharge
Level 44: Fire Shield
(A) Impervium Armor - Psionic Resistance
(45) Impervium Armor - Resistance
(45) Impervium Armor - Resistance/Endurance
(45) Impervium Armor - Resistance/Endurance/Recharge
(46) Aegis - Psionic/Status Resistance
Level 47: Vengeance
(A) Luck of the Gambler - Defense
(50) Luck of the Gambler - Defense/Recharge
(50) Miracle - Heal
(50) Miracle - Heal/Recharge
Level 49: Rise of the Phoenix
(A) Recharge Reduction IO Level 1: Brawl
(A) Empty Level 1: Containment
Level 1: Prestige Power Dash
(A) Empty Level 1: Prestige Power Slide
(A) Empty Level 1: Prestige Power Quick
(A) Empty Level 1: Prestige Power Rush
(A) Empty Level 1: Prestige Power Surge
(A) Empty Level 1: Sprint
(A) Empty Level 2: Rest
(A) Empty Level 4: Ninja Run
Level 2: Swift
(A) Empty Level 2: Health
(A) Empty Level 2: Hurdle
(A) Empty Level 2: Stamina
(A) Empty ------------
Now the Leadership powers are optional, but seeing as how you most likely would be grouping, they do help. The Fire Mastery Pool is just incase you want to make sure your Oil Slick ignites.
If you are looking for something more solo friendly Earth/Storm is quite beastly late game as well.