Yeah, we're talking end of... 3rd book I think? No worries and the actor who plays the imp is great. He does it pretty much perfectly.
I dunno about the whole length thing. I think it was always intended to be a long epic - he has mentioned going up to 10 volumes in total. I can't say I agree about the characters personally - the Imp and Jon Snow are still in the game

A favorite character of mine suffered a bit of a cliff hanger at the end of book 4... or a hanger anyway. I'm excited to see what happens to her.
As for the dragon queen being poorly written and mary-sue... eh. That's highly subjective. George R. R. Martin is no Patrick Rothfuss, Richard Morgan or Joe Abercrombie in terms of good characterisation, so... meh. As for Mary-Sue... She makes mistakes. One noteably HUGE mistake. She has flaws and while her road is in many ways paved for her... still. There are struggles. There are mistakes. There are sacrifices. As long as those are kept, to a large enough degree, then she's ok with me.
Of course, Bjørn and my taste in books differ in some points. I find Tolkien to ber exasperatingly boring and repetitive, R. Scott Bakker to be entertaining and gritty in a good way, etc. So this is clearly veering into subjective territory.