Don't get me wrong, I'm as pissed at C9 as everyone else; the premiere org that everyone looked up to as a pillar of NA esports ending up in the laughable state that its in is ridiculous.
That being said, I don't actually think C9 will perform that badly with two Tier-2 players to replace vanity and yay--and the only reason for that is mCe.
Remember, mCe is the one that brought together the original GUARD roster, finding virtually unknown players with a glimmer of talent and polishing them into undisputable tier-1 talent.
While it's obvious that C9 picked up runi and jakee to save money, I don't doubt that the one who actually chose those specific players was mCe, and a lot of their peers in the VCL have praised their talents.
Therefore, if there's anyone capable of turning these two into NA gods, it's mCe. Maybe not in their first few matches, but there's a strong possibility that later down the line, perhaps by champions, C9 might become a dark horse to win it all considering their current talent.
Hypothetically, if runi becomes an S-tier IGL, and jakee ends up being not only cracked but a team player (something the old C9 roster desperately needed), then Xeppaa, leaf, and zellsis will be able to reach their full potential but crush other NA teams given their raw mechanical and clutch skills.
If this is the case, I predict that 1 year down the line, the weak link will be Zellsis.