This item also drops on the third script in Inktu'ta - the cursecallers with loads of DT mobs running around everywhere while you kill the six named cursecaller mobs.
This is kinda stupid but the proc on it will have DMG increase from the focus effect being fire based and if you have all crit AA's you should be able to crit pretty good with this to lol just my 2cp =P
Procs can crit, but the damage focus doesn't work on them, at least not on 'instant' procs and not on clicky nukes. I understand that dot focii work on clicky dots, but I don't play a class with dot spells.
Focus effects work on spells that you can actually cast. For example, if a druid casts Swarming Death from a spell gem, focus effects work normally. If a druid clicks Swarming Death from the druid only range item in poTime, then focus effects still work, because it's a spell that his class/level could cast. Since no one can cast Tendrils of Fire, no focus effects will work on it.
What he means is that his intelligence WOULD BE 500, if the cap were that high. You can raise the stat as high as you like, but over the cap the only effect is to give you a buffer against effects that would lower the stat