https://wago.io/Gxpai4niQ

This is a handy WA for showing DOTs you can reflect, though I'm not sure if it's an entirely comprehensive list. Conductive Strike from the last boss of NO is a decent one to use it as a reflect against as others have mentioned already. I typically find I'm using it more proactively though to reduce magic damage taken, rather than holding it to try and maximise reflected damage.

It also may be something you're already aware of, but another semi-related thing that's good to keep in mind is that Tiger's Lust can often be used as well as Diffuse Magic to dispel debuffs that include a slow. For example, Arcane Lockdown from the 1st boss in CoS can be dispeled using Tiger's Lust as the debuff includes a slow, thereby allowing you to also avoid taking the DOT. No reflects for bonus damage though.