First question: How many times have you completed the Raid? Second question: What loot have you experienced from the Raid and on which characters? Here's the deal- If you've never completed the Raid on a character, then any secret chest is only going to drop Weapons. And any weapons you haven't discovered won't drop from chests. This is how I got Word of Crota, Abyss Defiant and Swordbreaker so quickly- Complete the Raid with one character only. If it's on rotation, farm 3rd or 4th until you get 1 WoC drop, so that you can focus it at the end of the Raid. Run Final Encounter every week. Pull your red border. It's a very easy encounter to coordinate with LFG. Every week hit the secret chest from 1st encounter with all 3 characters. The less loot you have pulled from the Raid in general, the better. Less loot dilution=more desired loot dropping. This would take a few weeks and you could very easily stack your Loot without crazy RNG. 5 weeks and you're guaranteed the weapon. Alternatively is using Deep Sight Harmonizers to focus the weapon along with Red Borders from Final Encounter. Regardless of how you achieve this Guardian, get in there and clear the Raid with the checkpoint bot, so that you can pull at least 1 red border. If you don't even have the weapon unlocked, you need to run 3rd & 4th encounter with all your characters one time (unless on rotation) and hope you get a drop to unlock it at focusing.

You could just wait till June when there’s a T5 version of it