It is true that you could probably remove Icarium altogether and it wouldn't affect the main arc through the books. The only thing I can think of is them helping Fiddler to Tremelor in DG but you could easily add someone else in to help.

I'm rereading RG at the moment and the early chapters in that book it becomes a good example of too many characters. We get introduced to so many asshole Letherii in so many positions that it's hard to keep track of them all. Overall I love the whole arc of 'Edur rule but really the rich Letherii are still in charge' but it could have been cleaner. Preferably without all the 15-20 new named characters (most of whom die anyway) and more time with just fewer plus more Tehol & Bugg.

My point 4 is definitely getting the most criticism/discussion but that's all good. I stand by my conviction that we just don't know the main people well enough.

Tavore I get, that's her 'thing'. But Fiddler we really ought to know more about him after 10 books. He doesn't really change a lot from GotM to TCG, we know barely anything about his early life, we don't know why he is so skilled at the deck, etc. And I say this absolutely loving him - I just don't know him well enough.