Cept you shouldn't spam Ruin 2... Once again, we have many more spells to cast depending on the situation, going into a ruin 2 spam is a waste of mana, a Diminishing return, and many other things you could do in a fight. I find it good to use in a whole I need to tag a monster way. Miasma 2 is another wasted cast as well...Do people actually use this on bosses?

I do Virus, E4AE, Rouse, Spur, Enkindle (300s cool down, blow it early to have it later.)
follow that with Bio 2, Bio, Miasma, Fester, Thunder, Bio again (will be nearly done by that time), Ruin, Fester and then back to the original rotation, adding Aetherflow in the mix.
If using Garuda, she'll refresh your Dots, giving you more Ruin casts....but seriously...DO NOT waste MP on Miasma 2 and Shadow Flare...especially using a Swiftcast. Save that for pet revival / battle rez.