Having two boards certainly makes this situation worse, although I do understand you are testing a new format.
Your players are everywhere, should you simply go everywhere they are and forgo a board completely? I illustrate this as an example to show how this is poor logic taken too far, IMHO.
Maybe use one site for announcements, news (twitter). I don't know man, this is Riot's job to figure out. Could be the format, could be the sorting, could be a problem due to voting. No clue, dude.
As for "Talk to us here instead of the boards" ..first of all, I can't recall where this was said, but I don't think its implicitness or explicitness matters in the end if the result is the same: having x number of sites which I as the player, have to keep track of them ALL, if I am intent on following up my feedback.
(Generally, people who give feedback want to know their concerns are addressed, so they will also tend to followup on said feedback.)
"Let's see, I made THIS point in the forums, do I need to repeat it on twitter, or did they already talk about this on the Dev blog?"
It should be streamlined. I feel like I should be able to say "I've already made my point, I can talk about this aspect of something now." Instead of keeping a journal of what was said where, who responded to it... etc. If the boards aren't the best way of reaching Riot, having a discussion, etc... then I, as a player, should not be the one to shoulder that burden. Look, I get you respond to players where they ask questions. I get you are passionate about the game. I don't know what the solution is, sorry man.
TLDR: I'm not like attacking anyone or what-have-you, I'm merely trying to convey how much of an inconvenience giving feedback can feel like.