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Maybe it would be better to have a small separate list of good utility Pokemon, unrelated to the actual tier list, similar to how in DPP they separated the Viability Rankings of Leads?
Doesn't Availability refer to when in-game you catch it, not how hard it is to catch? Also, isn't it around a 1/7 chance of 1%!Bagon summoning Salamence?
I don't think we should tier Pokemon factoring in their encounter rate, because it's entirely possible to get a Salamence as it's first...