I just hit 20 with drell vanguard too, even using the least accurate shotgun I still used +damage and +melee damage attachments instead of +accuracy. If you're trying super long range you're playing the class wrong, IMHO.
Play short to mid range, pulling everybody, finish with shotgun or melee, use charge to get a free shield regen when you need it or for when you've thrown something and you absolutely, positively want it dead NOW.
The nice thing about the "poor accuracy" of the shotgun is that you get headshots without even aiming at the head.
Oh, and all I carried was shotgun. The cooldown on pull was shorter than the travel time at mid range or longer. Final missions holding the pad before dustoff I would usually just sit back at the farthest cover and pull everything, let the rest of the team finish them off. It makes for really good crowd control in a situation like that where the people up front draw the fire and you don't have to worry about continually exposing yourself firing off one pull after another.
It was so much more fun to play than the human soldier I took to 20 previously. If people are playing human soldier first and not liking it much, CHANGE CLASS to anything else, you'll have more fun *and* probably move up on the scoreboard at the end of the round.