Pulled a pair and did some testing with them.
Testing was done in Lord of blades raid adventure area.
Character used 18 ftr/2 rog human stalwart 3
1st test:
S/B fighting style. Weapon used Epic Sirrocco w/ swashbuckler (low dmg weapon that allowed for more consecutive swings before mob died and also caused less incoming dmg due to trip effect so less time was spent healing. Haste up full time.
25 mobs killed.
30 average swings per mob.
total fabricator procs: 32
Fabricator procs per mob: 1.28
fabricator proc percentage. ~4.3%
2 chain procs (proc occuring before first wore off): 6 total
3 chain procs: 0
As a funny little side note I actually saw 3 blindness effects from sirocco meaning a failed save of a very low dc effect is more common than three chained procs.
Test 2:
Same character using TWF with all three feats. Weapon Set. Epic sirocco/Epic chaosblade. Haste up full time. Any mobs where I had to heal myself while a proc was active had that data discounted and isn't used in this testing. Two epic vorpals were discarded also.
Mobs Killed: 25
Average Swing per mob: 20
Total Procs: 30
Procs per mob: 1.2
Percentage proc rate: ~6% (Since I am getting 1.8 attacks per swing the larger number here makes sense)
2 chain procs: 6
3 chain procs: 1
Conclusions. The buff was up roughly 1/3 to 1/2 of the time it felt like in either style although it did seem a little more often in twf as it should. At this rate I have a hard time going along with the theory that it's better than the epic claw set (which I think it shouldn't be but I've heard this talk going around.)
+4 str is +2 dmg and +2 to hit but at only about 33-50% of the time fighting. The set bonus gives another +2 to hit and +2 dmg. Both have 20% incite.
So that leaves +2 exc con and heavy fort on claw bracers and 30% healing amp and 5 stacking intim on gloves.
The Fab set gives +2 to hit full time and another +2 part time which is relevant in some epic content. the 15 balance is really nothing significant just a nice perk. That means the fabricator's gloves had better be really really good if we are gonna see this replace a full claw set.
Now claw gloves epic gem of many facets and Fab bracers are an option but to have the fab set just outright replace the claw set both items for both is just pretty unrealistic claw gloves will still be in high demand.
The only other relevant argument is the bracers for an ac build. Now here it's most likely competing with the Tharaak bracersm I say this because if a character needs this for a +8 armor bracer slot then it's not an option at all). For a character at max dex bonus already this is pretty easy to always go with the +2 ac versus only part-time. Now a character without max dex bonus or not hitting full max dex (some characters are this way if using duealist leathers) its a full time +2 versus a part time +4, The part time +4 con is also really nice especially in the new raids where max hp values should be fairly high for a tanking character. All this being said the temporary nature of the buffs can be hard to rely completely on and +2 ac 50% of the time isn't enough to cover -2 ac the other 50% most likely. Mabar cloak and these bracers may be an option but then you start to nudge into the area of not being able to fit 3 pc abashai or other important gear too.