MAke sure you kick her as soon as her shields down to interupt cast. I didn't realise this on my first few attempts (should have found a better guide).
Make a macro to target Umbral Imps. In the end phases when you want to DPS her and they're shielding her then you'll want to find them quickly.
Aside from that, just take your time. Prioritise Imps and use Marked for death. Some people can use SND and Blade flurry but you need higher DPS output for that.