I find Selene fairly blah for low-level content since no one has high base Spell/Skill Speed, making her % buff even more marginal of an increase. The Silence is useful for a handful of fights, but you have to already know when you're going to need it since she may or may not already have another action queued when you want it. For higher level content I almost always run Selene just because that marginal buff is preferable to completely redundant healing; Eos stlll has a place for encounters where you feel that you require the extra cushion or where it's worth summoning her to help buff up for a mechanic that your progression group is just on the edge of surviving.

Sic is horrendous for Eos, sub-optimal for Selene. With Selene you can get away with it if you want, but I'd encourage you to get used to manually activating her buffs so that you can benefit from using Embrace manually as well. I use a keybind for both buffs so that I only have one key to press to cycle the appropriate buff.

You usually want to cast Bio last in your DoT opener if you plan to Bane since you will spread it with more time remaining.