The order is definitely not a waste. You mustn't rely on it to win you any games, but since you get it for free it is a nice little addition. It is of course best used with big lasgun squads when there are enemies within range of your lasguns and you want to shoots rather than run away (in which case I would recommend the "move, move, move!" order).
30 shots not killing a single marine is not too improbable. Statistically only one and a half marines will die on average, so none dying is just a little bad luck - it happens. If the hormagaunts had cover, killing six isn't much bad luck either with 53 lasgun shots: only 6.625 will die from that in cover on average.
The order doesn't turn flashlights into killing machine juggernauts, but it does increase their effectiveness by 50% in rapid-firing range or even 100% at long range. This is far from neglectable, and as I said: since you get it for free I don't quite understand the complaining.