1) Procs restore your temp items, also will terror a mob for 20-30s every time you hit something that gives a red!! - if you chain 3-4 procs in a row, you get a long time to do damage without needing to use defensive gear at all.
2) Check
https://www.bg-wiki.com/bg/Periapt for anything with temp items listed, you get KI's from various mobs in voidwatch. Most important are Fanatics Drink (Melee/WS Immunity) and Fool's Drink (Magic Immunity), both which last 60. As most highlevel fights are >60sec, it's important to restore these by hitting procs often.
3) During procs, you gain about 2.5% light of each color for every 1% damage you do to the mob. Basically it's a chance to get some red|blue light if the procs aren't easy/possible to hit from one side or another.
4) BRD is relatively easy long as you have decent sing/wind/harp skill - you need to be able to land threnodies, elegies, finale to proc. (Wind BRD <some number> means cast the wind-element threnody, not wind threnody. Look at the icon ingame) Depending on mob you might want to get fanatic's/fool's drinks pretty soon, since you'll need to run into aoe range to recast buffs.