I wonder how influential the Well of Sorrows will be. Morrigan repeatedly says how difficult it will be to process the information. If you let her and there is no Kieran, then you get a scene with her revelling in how much she now understands but she never divulges more than she has to. If you drink, then all you get from it is the ability to tame the dragon and to read a few old elven texts. If it was going to suddenly reveal all sorts of wonderful revelations about elven history, why didn't it? I suspect because they are going to say you were incapable of understanding what was revealed.
There is also the odd conversation with Solas after you get back. If you drink he goes on about how he warned you against it (possible because he knew he was going to kill Mythal?), although the writer admits that he forgot to put that conversation in at the Temple, so you only had that he didn't want to drink, which I must admit was sufficient to make all my Lavellans question the wisdom of doing so, along with the arcane knowledge of it being a geas and the less than savoury history revealed about the gods in the Temple. Cole also said that it wouldn't be a good idea to let all those spirits into your head. When a spirit tells you something is a bad idea, you really worry about the wisdom of doing it.
However, the strangest part is when Solas asks you what you are going to do with the Well, even when you haven't actually drunk from it. My latest run Morrigan had even told me that once Cory was defeated she was going to join the Warden in the west. So it was totally irrelevant what I wanted to do with the Well since Morrigan was the one with control over it. So I do wonder how important the Well can possibly be and that like the Dark Ritual, whether its relevance will be diminished over time. It was something you did, or Morrigan did, to stop Cory from getting it and give you an edge in the final battle with him, but thereafter it is not going to significant.