Yield depends greatly on the shield and laser settings. The only reason that one instance goes the way it does is because the shield were set to protect from a single direction, at full power, and the lasers were randomly sweeping the ground at maximum power trying to blindly roast stragglers. The single direction setting on the shield carried the most weight, usually the energy would be roughly evenly divided in all directions. In more standard fights with average shield use and laser settings, you are going to get a blast closer to a fragmentation grenade than a nuke. The biggest problem is it will happen at a completely random point along the beam, so it still isn't an attractive proposition.