i prefer to use bio first going bio - bio 2 - miasma.
this way i can cast bio twice within the time limit of rs, making opening looking something like this

RS - BIO - BIO 2 - MIASMA - RUIN 2 - FESTER - SWIFTCAST - SHADOWFLARE - BIO - CONTAGON

this way fester can be casted straight after miasma or bane in case of aoe and have bio put on for extra 18 seconds