I know how you feel, decisions are getting tougher. Took me a good while to figure out what I wanted to do but with Siani, my canon elf mage here's how it went down.
1) Siani drank from the Well. With all the unknowns she decided she should be the one to do it for Kieran's sake in case something went wrong she couldn't leave him motherless, the thinly veiled passive aggressive threat by my Warden in his letter certainly helped that decision.
2) Divine, I have softened Leliana. Just for my world state, it worked out the best.
3) Disband, in a wonderful aggressive fashion. "Now, if you'll excuse me, I have a world to save. Again."
Nothing against Leliana being Divine, love her, or the Chantry but after all the crap that happened in Trespasser Siani was done with the politics, people trying to use her, and not to mention all the spies. So she pulled in the ranks and decided only too keep the people she trusted in on the mission. Plus as he was part of her inner circle and love interest Solas is her responsibility, she doesn't want to sit way up above it all but handle it herself and hopefully stop him in time to change his mind.
All these decisions are very personal to the type of character and if metagaming (hard to avoid) the world state you wish this story to have.