Hey, I just quickly read over you build and there are several things that I noticed:
First of all, I see that you've only put one slot in Granite armor, which is really a shame since this is the main reason why Stone Armor tankers are considered to be such resilient to damage. I would personally suggest that you 6-slot Granite Armor with 3 resist damage IO's and 3 Defense IO's 
(you could maybe even throw a steadfast protection +3% defense in tough and you'd then already be over or very close to the soft-cap for all except psi-damage)
I found it also to be quite usefull to slot Teleport a bit more, certainly if you're teaming with a large group in a large map; at such times you'll teleport a lot, and a decrease in endurance cost/increase in range is definitely handy at those times 
Furthermore I think the other aspects of a stone tank are largely personal opinions; some people want to get a high runspeed, others would prefer to have capped out resistances + high defenses, and others try to get a lot of damage out of their stone tank and try to diminish their damage bonuses... It's all up to you I guess 
Hoped that may have helped you a bit
After getting my Stone/Dark Tank to 50, a friend of mine helped me come up with a build, and I was hoping to get some more feedback before I respec. I'm not looking for anything too fancy, although I'd be willing to spend a little more money if it'd be a big help. I plan to exclusively PvE, and would like to efficiently tank high level TFs (ex. STF, ITF, Kahn).
Hero Plan by Mids' Hero Designer 1.707
http://www.cohplanner.com/
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Camo the twink!: Level 50 Natural Tanker
Primary Power Set: Stone Armor
Secondary Power Set: Dark Melee
Power Pool: Fitness
Power Pool: Teleportation
Power Pool: Fighting
Power Pool: Speed
Ancillary Pool: Energy Mastery
Hero Profile:
Level 1: Stone Skin -- RctvArm-ResDam(A), RctvArm-ResDam/EndRdx(3), RctvArm-ResDam/Rchg(3), RctvArm-ResDam/EndRdx/Rchg(5), ImpArm-ResDam(5), ImpArm-ResDam/EndRdx(31)
Level 1: Shadow Punch -- P'ngS'Fest-Acc/Dmg(A), P'ngS'Fest-Stun%(11), P'ngS'Fest-Dmg/EndRdx(50), P'ngS'Fest-Dmg/Rchg(50)
Level 2: Earth's Embrace -- RgnTis-Heal/EndRdx(A), RgnTis-EndRdx/Rchg(7), RgnTis-Heal/Rchg(7), RechRdx-I(9), RechRdx-I(9)
Level 4: Shadow Maul -- Sciroc-Acc/Dmg(A), Sciroc-Dmg/EndRdx(11), Erad-Dmg(13), Erad-Acc/Rchg(13), Erad-Dmg/Rchg(15), Erad-Acc/Dmg/Rchg(15)
Level 6: Mud Pots -- Sciroc-Acc/Dmg(A), Sciroc-Dmg/EndRdx(31), Erad-Dmg(33), Erad-Acc/Rchg(33), Erad-Dmg/Rchg(33), Erad-Acc/Dmg/Rchg(34)
Level 8: Swift -- Run-I(A), Run-I(42)
Level 10: Recall Friend -- RechRdx-I(A)
Level 12: Rooted -- Numna-Heal/EndRdx(A), Numna-Heal/Rchg(34), Numna-EndRdx/Rchg(34), Numna-Heal(37)
Level 14: Teleport -- EndRdx-I(A)
Level 16: Health -- Numna-Heal/EndRdx(A), Numna-Regen/Rcvry+(17), Numna-EndRdx/Rchg(17), Numna-Heal/Rchg(19), Numna-Heal/EndRdx/Rchg(19), Numna-Heal(21)
Level 18: Taunt -- Mocking-Taunt(A), Mocking-Rchg(40)
Level 20: Stamina -- P'Shift-EndMod(A), P'Shift-EndMod/Rchg(21), P'Shift-EndMod/Acc/Rchg(23), P'Shift-Acc/Rchg(23), P'Shift-EndMod/Acc(25), P'Shift-End%(25)
Level 22: Siphon Life -- T'Death-Acc/Dmg(A), T'Death-Dmg/EndRdx(27), T'Death-Dmg/Rchg(27), T'Death-Acc/Dmg/EndRdx(29), T'Death-Dmg/EndRdx/Rchg(29), T'Death-Dam%(31)
Level 24: Boxing -- Acc-I(A)
Level 26: Tough -- RctvArm-ResDam(A), RctvArm-ResDam/EndRdx(36), RctvArm-ResDam/Rchg(36), RctvArm-EndRdx/Rchg(36), ImpArm-ResDam(37), ImpArm-ResDam/EndRdx(37)
Level 28: Soul Drain -- Sciroc-Acc/Dmg(A), Sciroc-Dmg/EndRdx(46), Erad-Dmg(48), Erad-Acc/Rchg(48), Erad-Dmg/Rchg(48), Erad-Acc/Dmg/Rchg(50)
Level 30: Weave -- GftotA-Run+(A), GftotA-Def(42), Ksmt-ToHit+(42), Ksmt-Def/EndRdx(43), LkGmblr-Rchg+(43), LkGmblr-Def(43)
Level 32: Hasten -- RechRdx-I(A)
Level 35: Granite Armor -- ResDam-I(A)
Level 38: Midnight Grasp -- T'Death-Acc/Dmg(A), T'Death-Dmg/EndRdx(39), T'Death-Dmg/Rchg(39), T'Death-Acc/Dmg/EndRdx(39), T'Death-Dmg/EndRdx/Rchg(40), T'Death-Dam%(40)
Level 41: Conserve Power -- RechRdx-I(A)
Level 44: Physical Perfection -- RgnTis-Regen+(A), RgnTis-Heal/EndRdx(45), P'Shift-End%(45), P'Shift-EndMod(45), P'Shift-EndMod/Rchg(46), P'Shift-EndMod/Acc(46)
Level 47: Focused Accuracy -- GSFC-Build%(A)
Level 49: Dark Consumption -- EndMod-I(A)
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Level 1: Brawl -- Acc-I(A)
Level 1: Sprint -- Clrty-Stlth(A)
Level 2: Rest -- RechRdx-I(A)
Level 1: Gauntlet
Level 4: Ninja Run