It's interesting according to DevBlog Missions revolve around SR due to majority
But somehow 5man Premade Mission will still stay, even If just in small frequency.
Like If you think you shouldn't do them often it seems majority doesn't want them, but you will desperately try to keep them, even If you try to make them "special" and "in small frequency".
But when it comes to mains of other modes, they can go fuck theirselves. With ARAM main or TT mains, they are just irrelevant minority so you will just revolve missions around SR, leave for others the little they can bend to other modes and not give a shit about us.
You could make permanent-mode-specific Missions also special or adjust requirements via OR condition, but no, we'll just not give a shit about ARAM and TT mains all-together, while still trying to somehow satisfy 5man premades.
The bias of that decisions just makes one vomit. If you can't even bring any creativity into allowing mains of other modes to participate just remove them and stop pretending something I guess...