The legality of blockers being in a passer’s line of sight really comes down to whether or not they moved to get in his way. Most teams go to great lengths to make sure there is at least one person between the opposing passer and his server to have a better chance of getting rid of his opponent’s offense, and that’s acceptable.
This situation becomes a problem when the service team observes you and actively moves to get in your way.
So a team can have their front line (and bottom line, for that matter) players set up in whatever way they see fit, as long as they are in the correct order / rotation. But if these players move with the purpose of blocking the view of the passers, then they have made a foul call, they should receive the ball.
If you have a problem with detecting the other team, but the referee doesn’t seem to notice, try exaggerating the problem by moving your head dramatically from side to side while trying to look around the other team’s blockers. Hopefully the referee will notice this and take note of whether the other team is actively blocking your server site. If he / she doesn’t realize it and is having real difficulties, ask your caption to speak to the referee.
However, this cannot be called on a server, and they can move where they want to make your life more difficult. Many servers like to position themselves behind as many of their teammates as possible for this precise reason, and that’s legal.
Good luck with your service and reception efforts. To see an illustration of the umpires’ calls for detection, visit volleyball-life.com.