I enjoy doing speedruns of the 140 Dungeons and helping out people in public lobbies. My favorite Dungeons loadout is:
Paleo Luna as my Commander.
And in support I use:
Tricera Ops Ramirez (any other dinosaur hero is fine)
Arrleen Izza (way more useful than Survivalist Jonesy in high PL zones)
Mainstage Quinn (you can easily get wafers from smashing the urns, and the RNG of the weapons in Dungeons basically necessitates wafers if you are running Paleo)
Crossbone Barrets (you can get coconuts by searching ammo containers and chests)
For gadgets I use Adrenalin Rush and Slow Field (very useful for minibosses).
In my weapon slots I have my melee, wafers, and coconuts.
Throw down a slow field, pop some wafers and coconuts as the need arises, and you can take out the minibosses with ease.