Yay for 3000+ pages! We've come a long way. 
Tempest trumps all! It's the most OP spec after Knight Enchanter, and that's not as fun to play. You just use Spirit Blade over and over again. Tempest though, freeze, slash, and burnination!
Nah, if you're a mage, you already have the option of freezing, electronuking, or burninating. And Fade Stepping, etc. Knight Enchanter just adds the baddassery of a lightsaber(!), phasing and nuking enemies from the inside out, possibly the best heal spell in the game, and disruption field for some force mage fun (EK *is* the spec with a lightsaber after all). 
Does the Sera=Andruil theory have anything to do with the Painted Box in First Enchanter Irving's Pimp Pad/Headmaster's office? I mean, the apparently unusually callous Red Jennies of Denerim threatened people over it, and it was in the same room as (an admittedly unknown at the time) artifact of the elven goddess Mythal.
Painted Box as a horcrux/fragment of Andruil's essence?
I'm just practicing my dart throwing here, don't mind me. 
In light of the fact that I had a dream I can barely remember that had something to do with raspberry jam, Sera, Iron Bull, and Andoral (which was the Archdemon slain by Garahel)...
The Painted Box is the thing about the theory that I wonder about the most, but as far as I know, it's the only thing I haven't seen really touched on. If there's any chance of the theory being true, I think this is most likely to be significant somehow. Even back in DA:O, I always wondered what in the world was going on with that quest. For some reason the Red Jennys are deadly serious about getting the box, and for some reason it's in First Enchanter Irving's office, along with Flemeth's grimoire. We deliver it, and there's nothing more said about it. Until Sera mentions a memory of playing with painted boxes during the time of the fifth blight.