There is only one way to make league of legends relatively impervious to DDOS: Peer to Peer
Peer to peer.
How do you administrate an authoritative state with a peer to peer model?
Bitcoin does it, so do something similar.
How do you secure the software on a peer to peer model?
Make the server executable arbitrarily divisible and many-fold redundant, then spread the pieces out across the network to be executed and checked via majority on the peer computers. Biological tissues perform a function well while being resilient to interference because they distribute the function among a large number of cells which check each other and who's behavior is largely modulated by the tissue itself, with very minor influence over the direct execution of the particular functions of the tissue from the other interacting parts of the body. The aggregate effect of that self checking is the ability to heal from damage, which is what you want in a peer to peer server model, so take hints from biology.
How do you control patches on a peer to peer model?
Implement a rolling backdoor.
Sounds complicated.
So what? You can't handle it? Bull****.