Sometimes you have to improvise, actually most times, you'll get those people that love to wake your sleeping targets, they tell you to sleep x role and the same person will first attack the person you just slept (even though they were the ones who told you to sleep them). Sleeps can be useful when you're not getting dogpiled and used on targets who are on your healer.

Spamming scathe won't kill the heals but it will make them run and putting them into LoS of their team, sometimes a pld or war will get on it to then you pop off blizz 1 or lethargy on the heals, and keep spamming scathe. If you can tolerate a lot of frustration that comes with playing a BLM you should be fine.