A book is a much different medium than a moba. If Harry dies, the series can continue as is with no problems.
Lets say that Ashe dies, LoL cannot continue like that.
"Why can i play Ashe? Isnt she dead?"
Or
"Im one of the four people who plays Ashe, why was she removed??"
Asking for 'endings' in League just does not make any sense. Here are the three options for the Freljord war, Khazix/Rengar, Lucian/Thresh: you can have non-decisive ends (like Tf/Graves), one murders the other or they stay as they are un-concluded-ified?
If all four stories (including Tf/Graves) all end up with the parties shaking hands, understanding their differences then parting ways, how incredibly lame would that be?
Or they murder each other and we have champions in game specifically removed from lore, how silly is that?
Or understand League as a moba can only tell stories from past to present with no endings