If you're wondering how there could be so many cheaters...
or doubt that there are, or doubt that there are lag switchers than I present you with this website. Specifically this device which has a specific setting for Destiny. It also allows people to use a Mouse and Keyboard. So if you're wondering how someone can go flawless in trials while having a 10+ k/d ratio (the average across all of Destiny is 1 and the best players I've seen usually hover around 2-4) then this is it.
An excerpt from the site, "The Titan One has 12 different mod classes with up to 53 selectable mods allowing for millions of mod combinations giving you a fully modded controller with no installation necessary. You can choose and combine one mod from each class for a total of 12 active mods at the SAME TIME. This means you can make combinations such a burst fire added to rapidfire resulting in an exclusive "automatic burstfire" mode. This mode can be optimized by adjusting the number of bullets fired per burst as well as the time between bursts. For additional optimization, you can add the "scope enable" mod which will allow your "automatic burstfire" to be activated only when the ADS scope is in use."