If you've ever watched Alton Brown you would know that searing it doesn't seal in anything, it just adds a layer of flavor.
As for burgers, IMO there is no "wrong" way to do a burger. Sometimes I like a griddle burger just because of the hard layer that forms on the top and bottom, sometimes a quick pan fry is in order for a simple hamburger steak, other times the small gas grill gets fired up just for poopz and grinz. I've even done burgers in the oven before. Though my favorite is cooked over 100% hardwood coals, don't get to do that often so I usually settle for briquettes.
When I get enough spare cash laying around, a Traeger is going to be coming home for sure. But not until I buy a good dedicated smoker.