Overview
德利尔 is a burst support RF.
德利尔’s kit revolves around Critting on a target 15 times, cleansing and debuffing that target, and then applying a big Vulnerability debuff on them with her active Skill. Obviously, this means she is an extreme single-target specialist. Note that 德利尔 doesn’t really do a lot of damage herself, she simply enables an actual strong DPS to nuke that one target.
With this in mind, it should be clear that 德利尔 is very niche. She specializes in very specific single-target speedkill situations, and is absolutely not a general use RF or even a “general bossing” RF (which does not exist).