Channel abilities like Miss Fortune R or Karthus R are terrible in this game for 2 reasons:
- They are anti-synergistic with attack speed, the core mechanic of the game by which ALL champions deal damage and gain mana to cast their spell. The longer units spend not attacking, the less mana, the less times they cast their spells, the less damage. Aurelion Sol with a few items deals maybe 2 to 3 times more damage than Miss Fortune on average for that reason, he casts his spell 2 to 3 times as much as her. (MF AI is also trash btw)
- They can be interrupted. Which brings us to my title. Since most champions start the game with roughly the same amount of mana and gain mana at the same rate, most champions will use their spell at roughly the same time. When that happens, channel abilities will always be interrupted by other slightly delayed crowd control abilities, like Sejuani or Pyke or Kennen or Gnar or Chogath, or Glacial etc. They can also be interrupted by champions getting killed but that's another issue.
With my proposed change, units with channelled abilities can at least expect to cast their abilities once per fight given the right circumstances.