The legality of blockers being in line of sight of a passer really comes down to whether or not they moved to get in your way. Most teams go to great lengths to make sure there’s at least one person between the opponent’s passer and your server to give them a better chance of deflecting their 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.
Thus, a team can have their front row (and back row, for that matter) players set up however they see fit, as long as they are in the correct order/rotation. But if these players move in order to block the view of bystanders, then they have committed a foul and you should receive the ball.
If you have a problem with the other team’s projection but the referee doesn’t seem to notice, try to exaggerate the problem by moving your head from side to side while trying to see around the other team’s blockers. Hopefully the referee will notice this and take note of whether the other team is actively blocking their site from the server. If he/she doesn’t notice and you are in real trouble, ask your subtitle to talk to the referee.
However, this cannot be called on a server, and they can move wherever they want to make your life more difficult. Many servers like to position themselves behind as many of their teammates as possible for this exact reason, and that’s legal.
Good luck with your serving efforts. To see an illustration of referee calls for evaluation, visit volleyball-life.com.