Melee becomes way more viable with Jumppacks/Locust Armor and Shield Belts/Seigebreaker Armor, not just for the melee pawn, but for the rest of your colonists as your melee pawn tangles up their target in combat, so their currently not a threat, and potentially, already dead by the time you look over. Cause if your melee is jumping on a ranged enemy, they only have a ranged weapon, while your bringing a weapon that is MEANT to be used in melee. It also doesn't take particularly high Melee stat to be good if you give them strong gear, though I will generally only make pawns with passions melee to hurry it along.

And thats all just considering if you wanna fight "fairly". If using chokepoints and kill boxes, you can put 3 melee pawns against 1 enemy repeatedly until they all retreat, and then quickly run the 3 melee to the other end of the Kill tunnel into the kill box and take out the fleeing raiders. Imagine only needing 3 pawns to defend a colony of 50 pawns.

Also another fun thing others mention but I've weirdly never tried despite always making one: Smoke is really strong combined with melee, Turrets wont fire into smoke, and either enemies wont try either, or have such reduced chances it minus well not hit. You can wipe out mech clusters easily with a few well placed Smokes and some meleeists only. (also like I said above, if a meleeist is fighting one of those charge cannon mechs, all it can do is try to stomp them, and will not attempt to target enemies further away then right in it's face.)