A lot of people blame gear when they should be blaming lag. Gear doesn't matter as much as people think it does (especially low level players - their abilities recharge at a faster rate I think. discipline,strength, etc boosting their recharge times on a different scale)
also, some weapons handle differently. i had the biggest discussion with a friend of mine today about weapons only to realize that he had no idea that you have to lead your targets with the fusion rifle. you can essentially 'drag' the FR to spread the blast with it. there are plenty of nuances like that in the game. the trigger squeeze being a noticeable deal for some weapons as well.
about shields... yeah, some of it does have a definite advantage in terms of the added perks - but its no different than a level 20 sizing up a 6th prestige guy in CoD. They're not Gods by any means. Just stack the deck in your favor and use your map awareness to not be in positions where you're in a fair fight with those guys while they're supercharged. (even then, a few more shots kill them just as easy). those aren't usually gear related though.
armor/restoration/agility DO matter, but having high armor and no speed means you're just an easier target while you're alive in on spot. and good luck chasing anyone or anything down on top of that. i ran basically pure speed builds with my blade dancer and straight crushed people because i could hop in, fight, hop out and regen, then hop back in faster than anyone else.