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Bloodthirsty is a boost to damage after all buffs.
So yes BT scales with proc sets, but proc sets do not scale with BT. So you will never see BT effect your dmg in the tooltip for your armor - but the effect of the dmg will.
I would hope that the scaling of proc sets would take Bloodthirsty into account, just like abilities that scale off stats. You won't see it on the tooltip of the ability, but if the enemy is below 90%, they will take the extra bloodthirsty damage. Proc sets should work the same. The only way that Infused would be better is if proc sets ignored Bloodthirsty completely, which would be disappointing. Has anyone tested this?
I believe it does work with proc sets, in the patch notes there they mention changing Relequen dmg ticks to take the current WD instead of the WD when you first apply the proc effect.
The difference is that BT scales based on missing health, from 60% health it outperforms Infused. For sets with AOE procs I am not sure if mobs with different health levels take different amounts of dmg for example.
The main thing to consider here, imo, is do you want more upfront damage (like for mowing down hordes of weaklings when farming XP / normal dungeons / vet add pulls / etc.) or do you want more damage ramp up toward the end of longer / tougher fights (like bosses mainly)?
You don't need to do specific in-depth testing to know which you prefer for your build or play style or whatever, and that's mostly what Infused vs Bloodthirsty really boils down to in the end.
For organized group content where your job is dealing damage above all else, Bloodthirsty is the way to go. For pretty near everything else, it's either a toss-up that you can decide based on sheer preference, or Infused comes out ahead. (Only comparing Infused vs Bloodthirsty here, of course; other traits are good for other builds and whatnot, but that's off-topic.)
But fwiw, Infused is a bit more versatile in that you can swap Glyphs around as needed without leaving the instance you're in, which can come in handy on occasion (like if your group isn't helping you with sustain enough and you need a Recovery boost on the spot). It's also better than Bloodthirsty for boosting non-damage skills, like Vigor and whatnot. Not having to rely on fighting some low-health target for your power boost is nice in a lot of cases. But this mostly applies in random groups, solo, etc.