Removing RNG
How would you do that?
Imho:
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Zoe: minions don't drop spell shards anymore (was it even needed in the first place? if she ends up suffering too much for this, just give her some compensation buff)
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Dragons: make their random order known from champ select. This way they are still random, but it's a kind of random that can be strategized with/against.
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Crit: eh, this is a tricky one. Let's see... as a role, ADCs are supposed to provide sustained DPS. The goal, to provide the damage to kill tanks and take objectives. Mmm... what if they were split into 2 sub classes? On-hit adcs could focus on tank-shredding and objectives, with AS and %HP damage, while ranged casters could focus on CDR and AD for either AoE damage or single target burst (like mages do). This way crit could be removed altogether as a mechanic, while preserving the role of ADCs. Some champs that would end up as on-hit adcs:
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Some champs that would end up as casters:
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Afaik there are no other random mechanics in the game.