It’s not practical to craft 418 gear with mats from the mythic raid.
You would have to go at a minimum 5/8 mythic every single week since launch just to keep pace with sparks.
Also, tier is a guaranteed drop from tier bosses, it’s just RNG in who gets it.
But for a consistent group it’s guaranteed tier to the team every kill.
Targeted slot (aka weapons) 418s with perfect stats is really good, don’t undersell that.