Thanks. I don't know what a worn focus is but I'll look out for it at higher levels. It can be tricky pulling if you don't have see invis.
Deadeye at level 17 provides see invis: http://everquest.allakhazam.com/db/spell.html?spell=352 Cloak of Shadows is invis, not see invis.
If you use Defiant gear, it provides see invis starting lvl 48, with Intricate. (Effect: Plainsight, Ultravision + see invis) Starting with Elaborate (lvl 59) pretty much all headgear has 'Faerune' which combines See Invis, Ultravision and Water Breathing. Note there are some mobs that get an upgraded invis, and require a special see invis spell (i.e. Druid 'Eyes of Winter Hawk)