That's because engineers have ridiculous shielding.
The only way someone is going to deal anywhere close to 50% damage to you is if they are getting a melee exploit attack, and if they get that they deserve the damage. They are very difficult to pull off.
I don't do allot of ground PvP, mostly because ground combat is so broken. But I can say there is too much melee in PvE as well. Now i expect the occasional Kilingon or borg to try to get up close but many if not all of the races do it. It's annoying and frustrating, get out of my face already. And this isn't a hack and slash type mmo. While there was plenty of melee scenes on the show, never did enemies run through an onslaught of phaser fire to melee someone (besides the borg). I mean that is just stupid AI imo, and if that is going to happen there should be a penalty for it, such as more damage the closer they get with ranged weapons.