I had a couple of people inquire about leveling in a primal sphere and whether that would still be viable. It is viable, you do lose 1 DC but you do offset it with wis and also pick up spell power and a additional 44 ranged power to augment you ancilliary damage. This runs in Primal avatar, in some ways it is more durable then the EA because of it's mitigation and greater healing as well. I enjoy both versions depending on my mood.
Because of some test bed results we have been getting back in the last couple weeks from people running GTs at various levels I've made some small adjustments to the overall build and it's cycles. By and large we have dropped Manyshot from the Terror cycle and are only using it in fairly specific circumstances where the 4xranged power is going to create benefits that off-set it's sub-par Vorp proc rate. Bosses, portals, etc.. And the occasional use to proc a action boost while the GxB's reinvigoration is on timer. I have also changed out a feat and some twists.
Here is The GTP, AKA: The Great Terror Primal.
As the GT I developed this build to exploit the GxB's expanded vorpal range (19-20) with AA Terror effects, take advantage of the GxB's abberant endless fusilade ROF(26 bolts per animation), the GxB's Large Base buffed by +4[w] (giving 9[2d8] at endgame), mechanical reloader speed boost, Ranged Power amplified Sneak attack dice, and alternating IPS/Archer Focus to maintain heavy Mech DPS while still achieving very frequent DC87 insta kills.
The Build exploits the GxB Terror vorpal range of 19-20. By using the chain of: Endless-fusilade* 23 seconds Normal GxB fire*Endless-fusilade, it achieves a 37 second burst that produces a PK kill every 3.2 seconds at a DC of 87. During Endless fusilade itself the build produces a 7 second bursts of PK kill every 2.3 seconds or by running without any boosts a normal rate of 1 PK kill every 4.3 seconds. Of course running with and utilizing IPS properly will exponentially increase all those proc numbers as each additional target strike uses the doubled Vorpal range to PK twice as often. Also of note, if Manyshot is used 2nd during an attack chain the second Endless Fusilade can be started the moment Manyshot ends. The 1 second EF prep animation runs concurrently with the weapon switch, resulting in a quicker EF start as well.
Outside of PK kills, the running Mech DPS is high due to 14-17D6 Sneak Attack, +4[w]GxB, +16GxB Damage, 30% reloader speed, Mech tree ranged power, expanded Vorpal and the Runearm damage, scaling Runearm primary damage, and runearm charge and cooldown buffs, imbue increase and critical buffs.
Through enhancements and Epic destinies the build runs with 11 boosts of each type, these add Wis, Damage, and most importantly the GxB Endless Fusilade. With auto reloader, Blinding speed working the Endless Fusilade of the GxB will fire 26 times in the time it takes the 7 second animation to start and end. That is only one less than the 27 of the light repeater, but with vorpals on 19-20s.
The Great Terror build is very Past Life dependent. You will need them for DCs, doubleshot, Hamp, Pos, HP, etc.. You will also need Epic past lives for both fate points and twists. You must also choose your active EPL & IPL stances wisely, it benefits greatly from +6 tomes but can be run with +5s.
Closely following the Class progression and Stat bonuses is important so that you are able to secure the full list of needed Feats at level with prerequisites. For instance you must start with Artificer to access Enchantment focus early, so as to free up slots later.
The GT can be run by other races but it will be at a loss to DPS and DC due to Wisdom bonuses and Feats. Over the weekend I did run and test a Deep Gnome version. Using DG you will have a 1 higher wis, +2 dodge, +4 MRR but to acquire manyshot you end up taking more Ranger levels at the cost of 2d6sneak, damage to Xbows and 20% damage boost.
The Great Terror Primal~
Human 12Rogue/4Ranger/4ArtificerStr 8
Dex 15 - +5 tome
con 14
Int 14
Wis 18 - +5 tome
Chr 8
All level-up bonuses to wisdom except for level 20 which is Dexterity, for Epic feats.
Level progression: 1Arty, 2-5Ranger, 6-16Rogue, 17-19Arty, 20Rogue.
Feats:
1) Point-blank
1) Enchant focus -
human extra1) Proficiencies GxB,repeaters-
Free Artificer feat1) Rapid Reload-
Free Artifcer feat3) Completionist
3) Rapid Shot-
Free Ranger feat5) Precise Shot-
Free Ranger feat6) Past life, Wizard
7) Evasion
9) Past life, Bard
9) Uncanny dodge-
Free Rogue feat12) Greater Enchant focus
13) Improved Uncanny Dodge-
Free Rogue feat15) Many shot
15) Improved evasion, -
Rogue bonus feat16) Runearm use -
Free Artificer feat18) Improved precise shot
19) Improved Critical Ranged weapons -
Free Artificer bonus feat21) Combat archery
24) Embolden spell
26) Positive spell power
27) Blinding speed
28) Doubleshot
29)
Arcane Warrior (different from normal GT)30) Epic sneak Attack (or Arcane insight if you need DC boost)
30) Scion of the Feywild
Enhancements:

NOTES: I avoid buying the Battle engineer damage boosts because currently the BE boosts are bugged so that they do not activate the Human Action surge that the build utilizes for +2 wis. If they are ever fixed I would purchase damage instead of runearm buffs. On the AA Tree, I occasionally trade Awareness for True strike. Other than the Wis in AA moving over to action surge for 1, there is not a lot of room to move points around and still achieve the Build's purpose. Terror is the best bang for the buck currently as the non-vorpal scare effects everything it doesn't PK. No spell resist to AA arrow effects and the 3 second cool down on the Dispel shot means you can drop Mob deathwards constantly while getting another +4d8 damage.

Epic Destiny:
Primal Avatar, all wisdom, spirit boon (mental),cocoon, insidious spores and tsunami for Arcane warrior, take your pick of either PRR or dodge. I dropped 1 point into summer smoke here but it could have gone in dodge. You also pick up 24 additional ranged power for free with Primal, combined with Arcane warrior that's a additional 44 points of ranged power, which can be good to have for bosses and rednames. I only put 1 point into insidious spores because I'm not using it for damage but to build stacks for Arcane warrior in combination with the runearm. The range on Spores is really large as well, making it easy to use, but due to it's nature most mobs ignore at least half of the damage (rust), more ranks wont lower the sp cost so just one will due.
Additional Destiny notes:
Primal's Spirit is proc'd both from the attack and the Terror effect so it's very quick to fill 30 spirit and and you can use that to maintain the cores of 'eternal return' for 90 seconds, or even 'walk with spirits' for 44 seconds.
Twists
'Primal travel''s 50% dodge boost stacks with Improved uncanny dodge for only 1 spirit you will be at 100+ dodge. 'Walk with spirit' will make you invisible, ethereal, and 25% incorporeal that incorporeal stacks with other forms like the LGS incorp % for a stacked 39%, while running the GTP you can maintain that for 44 seconds before running out of Spirit. The best part is it's cooldown is only 5 seconds so you can pop it off constantly.
-
Echoes of ancestors, shiradi champ: 10% stacking ranged speed replaces Pierce the gloom-Enchant school
-Draconic presense
-3 extra action boost (LD, not shown in pic)
-Don't need cocoon on Primal build.
ARCANE WARRIOR FEAT, By spamming the insidious spores along with the tsunami and entangle I can get 20 and maintain 20 stacks of the Arcane warrior's Ranged power boost, the spell power is constantly filled due to ranged fire so that benefits my Rune arm quite a bit. Additionally I can start-spam the bee shot on Machine of madness and that will proc the Arcane warrior buffs as well, which the Archon runearm wont, so good reason to go with the machine of madness.
Terror Arrow-DC Calculation:
1 Enchant focus
1 Great Enchant focus
1 Wizard PL
1 Bard PL
2 Embolden spell
4 Scion Feywild
1 AA terror
1 primal spirit boon
3 Enchant specialist
3 Draconic pressence
1 Profane DC
2 Enchant insightful
6 Enchant Competance
2 Enchant Greater Augment
1 Guild ship
______
30+20+31(wis)= 81 (87 with Arcane insight)
Yes, I could easily get higher with Bard song, lit, etc.. this is just where I am now and can maintain solo or in groups.
Ranged power:
20 Mechanic
30 epic levels
24 Primal levels
20 Arcane warrior
4 mythic
_________
98 STANDING RANGED POWER
45 Archer focus
20 Quality (I can run my Toee set, but prefer other, better gear)
_________
163 LIFTED RANGED POWER
80 Manyshot (4Xbab)
__________
243 MANYSHOT STANDING RANGED POWER
Luckily because of the very large base damage of the GxB mechanic combination, all the Sneak Attack Dice, and the extra 540 damage a second the Runearm spits at 300 spell power the build doesn't have to use the 'lifted' or other stance very often as it's Boss and redname DPS is so high.
Final thoughts, I really liked the various builds that tried to use the changed AA imbues, but in every case I found that the procs didn't come anywhere near fast enough and the damage in between those procs or against red-names totally sucked to the point of making them useless overall. I tried many different variations before landing at the GT's fine balance of constant insta-kills and heavy boss dps. I have to admit that I was really surprised to find that in the end the build that could spit out the most procs per second was also the heaviest non-proc damage. I had tried bow, repeaters, and monk chucker builds and none of them could match the Proc rate, and only the chuckers came anywhere near the DPS. Between the EF's vorp every 2.3 seconds and the normal fire's vorp every 4.3 the PK rate just can't be matched.