BW Light is good for assistant healer mages as light armour, not for an archer.
If you are into PvE get Plated Leather and don't look back till you have Majestic...B grade sucks for an archer, except for the Bow of Peril.
/agreed
Doom Light gives you more Dex, which improves crits, attack speed and movement. But I think PL set is still the best way to go at B grade. Start saving up for your Majestic LA set.
If you wear the heavy armor you lose a fair bit of evasion and weight will really hurt your ability to carry arrows and SS, being human with higher carrying capacity you might get away with it. But by the time you hit B grade you are starting to get enough light masteries I don't think the heavy armor would give much higher overall defense (again with a lot lower evasion). It might trick some into thinking you are not an archer thus buying you time in PVP though...