Warband map mod from zana

I don't quite understand how this works in terms of tiers. Do i still have to kill a certain amount of them in the same tier of map to get the higher warbands to spawn or is it just luck in what warbands spawn?

Should i be checking all the blues that drop or am i wasting my time looking for the league specific mods? I read that there would be a mention of what type of warband would be in my map in text form but all i saw was 3 warbands are inside this area. Is there a way to tell what warbands i got prior to finding them or do i have to figure it out based names and skills they use?

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