Unless there are a buttload of targets, delaying bane for Shadowflare doesn't make sense.

Bane is 110 ppt, Sflare is ~37 ppt.

Delaying Sflare till after bane costs you roughly 2 ticks, this is 75 or so potency.

Delaying bane till after Sflare costs you 1 bane tick, which is 110.

At roughly 6 targets sflare beats out bane for delay.

Sflare should be delayed from single target opener because of RS usage, for a quick fester into contagion.

General rule of thumb for trash is, refresh DoTs if target is at >50% health, refresh only bio if between 20 and 50%, and don't refresh DoTs at 20 or lower.

One thing you need to remember: if you're using garuda (and you should be using garuda), and you have her on obey (and you should have her on obey), make sure to manually use her aerial slash on cooldown for AoE.