Here are two absoultely awesome powers to deal with Borg. If you are a Sci, then grab the Physicist Kit. If you aren't a Sci, then be sure to bring a Sci BO with these powers.
Electro-Gravatic Field (formerly Gravitic Shift) - This holds a group of Borg in a single place.
Exothermic Induction Field (formerly Thermal Vent) - This deals AoE fire damage in a single place.
HIt EG field to hold them, then EI Field to burn them. You can pretty much one-shot most borg after doing this to them.
Another recommendation is to have 2 different Sniper Rifles. Just use the secondary attack to deal sniper damage. Snipe, switch weapons, backpeddle a bit if needed, then snipe again. This way you spend alot less time remodulating.