Apparently people who do kill stuff aren't coming here as such, and it is merely a matter of other people reporting it. Interestingly the datamining hasn't uncovered the various bonuses (yes, it is bonuses, and not boni in English).
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I asked on the webpage at Irae Aod, and they reported that the "boni would similarly to boni in WoW modify existing skills, for example the Smuggler Healer Set Bonus makes the AOE Heal cheaper". Sadly they did only tell this little teaser ;-) At other places I read claims set boni would be at 2-set and 4-set which would mean you could use 3 off-set-pieces if this is true (if this is true, this would be great news from a "no clones" perspective).