Ugh, this attitude. OK, so maybe Lavellan's not immortal and magical and covered in glitter, but if one of you god-like jerkfaces would get off your high horse and EXPLAIN it to her, she'd understand? Of course no one's going to know anything if you just keep it all to yourselves 
I feel you. This is the single most frustrating aspect of DAI for me. At least Mythal doesn't turn up her nose at the Dalish like SOME OTHER ELVES (*coughsolascough*) but STILL. Here the elves are, thinking their gods left them because they did something wrong and if they just do the right magical things that the gods will come back (at least this is what Merrill says) and one of the gods IS TOTALLY CHILLING OUT in the woods. And she's not above using the Dalish to ensure her survival (Apparently she made an exchange for that but we're never told what it is). So what is this? What the heck is going on here that she can't be like, "Yo, I'm here but your ancestors murdered me and I'm not helping you anymore." Or "Hey I'm not really that powerful so I'd love to give you a hand but I can't really so good luck."
I don't know what happened with Solas. According to him, he tried to tell the Dalish some stuff, but who knows what it was or how he went about it. And why he won't tell Lavellan this stuff - when she seems totally open to it - is beyond me. Is it because he doesn't want her to worship him? Is it because he is afraid he'll reject him? Is he just being a snob? I don't know. No one tells Lavellan anything. I get that it's a necessity for the story - you couldn't tell JUST F!Lavellan's critical info - but come on. COME. ON.
Same here. Every time Solas and Mythal give some vague and/or cryptic warning that the elves' past is not as wonderful as the Dalish have romanticized it as, I just want to turn to them and say, "Is there something you'd like to share with the class?"
Solas is so snide about the Dalish's limited knowledge and understanding of their own history, and doesn't hide his contempt when the Dalish PC shares the stories she's heard. I just want to say, "If you know better, I'm all ears (as we elves like to say)." When Mythal reveals she's been awake and around for centuries but hasn't made herself known to or helped out the elves, and when called out on it cryptically says, "You know not what you ask," I want to scream, "THEN WHY DON'T YOU EXPLAIN IT TO ME?!"
Ignorance is cured with education, not condescension.
EDIT: Although I do kind of love how Morrigan and Female Lavellan both call Flemeth/Mythal out on being such a horrible maternal figure. Morrigan calls Flemeth out for being a terrible mother, and Lavellan calls Mythal out on being a terrible goddess who abandoned her people.